On Tue, Sep 24, 2024 at 04:30:06PM +0000, Matthew Brost wrote:
> On Tue, Sep 24, 2024 at 12:42:56PM +0200, Thomas Hellström wrote:
> > Hi, Matt,
> >
> > Some random review comments on this patch I came across while looking
> > at multi-device.
> >
> > Thanks,
> > Thomas
> >
> >
> > On Tue, 2024-08-27 at 19:48 -0700, Matthew Brost wrote:
> > > This patch introduces support for GPU Shared Virtual Memory (SVM) in
> > > the
> > > Direct Rendering Manager (DRM) subsystem. SVM allows for seamless
> > > sharing of memory between the CPU and GPU, enhancing performance and
> > > flexibility in GPU computing tasks.
> > >
> > > The patch adds the necessary infrastructure for SVM, including data
> > > structures and functions for managing SVM ranges and notifiers. It
> > > also
> > > provides mechanisms for allocating, deallocating, and migrating
> > > memory
> > > regions between system RAM and GPU VRAM.
> > >
> > > This mid-layer is largely inspired by GPUVM.
> >
> > NIT: Naming, Should it be drm_svm rather than drm_gpusvm? For the
> > drm_gpuvm component, gpuvm clearly distinguished a gpu_vm from a
> > mm_struct but here we don't have the same need.
> >
>
> Can rename.
>
> > >
> > > Cc: Dave Airlie <airlied@xxxxxxxxxx>
> > > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > > Cc: Christian König <christian.koenig@xxxxxxx>
> > > Cc: <dri-devel@xxxxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> > > ---
> > > drivers/gpu/drm/xe/Makefile | 3 +-
> > > drivers/gpu/drm/xe/drm_gpusvm.c | 2174
> > > +++++++++++++++++++++++++++++++
> > > drivers/gpu/drm/xe/drm_gpusvm.h | 415 ++++++
> > > 3 files changed, 2591 insertions(+), 1 deletion(-)
> > > create mode 100644 drivers/gpu/drm/xe/drm_gpusvm.c
> > > create mode 100644 drivers/gpu/drm/xe/drm_gpusvm.h
> > >
> > > diff --git a/drivers/gpu/drm/xe/Makefile
> > > b/drivers/gpu/drm/xe/Makefile
> > > index b9670ae09a9e..b8fc2ee58f1a 100644
> > > --- a/drivers/gpu/drm/xe/Makefile
> > > +++ b/drivers/gpu/drm/xe/Makefile
> > > @@ -25,7 +25,8 @@ $(obj)/generated/%_wa_oob.c
> > > $(obj)/generated/%_wa_oob.h: $(obj)/xe_gen_wa_oob \
> > >
> > > # core driver code
> > >
> > > -xe-y += xe_bb.o \
> > > +xe-y += drm_gpusvm.o \
> > > + xe_bb.o \
> > > xe_bo.o \
> > > xe_bo_evict.o \
> > > xe_devcoredump.o \
> > > diff --git a/drivers/gpu/drm/xe/drm_gpusvm.c
> > > b/drivers/gpu/drm/xe/drm_gpusvm.c
> > > new file mode 100644
> > > index 000000000000..fc1e44e6ae72
> > > --- /dev/null
> > > +++ b/drivers/gpu/drm/xe/drm_gpusvm.c
> > > @@ -0,0 +1,2174 @@
> > > +// SPDX-License-Identifier: MIT
> > > +/*
> > > + * Copyright © 2024 Intel Corporation
> > > + *
> > > + * Authors:
> > > + * Matthew Brost <matthew.brost@xxxxxxxxx>
> > > + */
> > > +
> > > +#include <linux/dma-mapping.h>
> > > +#include <linux/interval_tree_generic.h>
> > > +#include <linux/hmm.h>
> > > +#include <linux/memremap.h>
> > > +#include <linux/migrate.h>
> > > +#include <linux/mm_types.h>
> > > +#include <linux/pagemap.h>
> > > +#include <linux/slab.h>
> > > +
> > > +#include <drm/drm_device.h>
> > > +#include "drm_gpusvm.h"
> > > +
> > > +/**
> > > + * DOC: Overview
> > > + *
> > > + * GPU Shared Virtual Memory (GPU SVM) layer for the Direct
> > > Rendering Manager (DRM)
> > > + *
> > > + * The GPU SVM layer is a component of the DRM framework designed to
> > > manage shared
> > > + * virtual memory between the CPU and GPU. It enables efficient data
> > > exchange and
> > > + * processing for GPU-accelerated applications by allowing memory
> > > sharing and
> > > + * synchronization between the CPU's and GPU's virtual address
> > > spaces.
> > > + *
> > > + * Key GPU SVM Components:
> > > + * - Notifiers: Notifiers: Used for tracking memory intervals and
> > > notifying the
> > > + * GPU of changes, notifiers are sized based on a GPU
> > > SVM
> > > + * initialization parameter, with a recommendation of
> > > 512M or
> > > + * larger. They maintain a Red-BlacK tree and a list of
> > > ranges that
> > > + * fall within the notifier interval. Notifiers are
> > > tracked within
> > > + * a GPU SVM Red-BlacK tree and list and are
> > > dynamically inserted
> > > + * or removed as ranges within the interval are created
> > > or
> > > + * destroyed.
> > > + * - Ranges: Represent memory ranges mapped in a DRM device and
> > > managed
> > > + * by GPU SVM. They are sized based on an array of chunk
> > > sizes, which
> > > + * is a GPU SVM initialization parameter, and the CPU
> > > address space.
> > > + * Upon GPU fault, the largest aligned chunk that fits
> > > within the
> > > + * faulting CPU address space is chosen for the range
> > > size. Ranges are
> > > + * expected to be dynamically allocated on GPU fault and
> > > removed on an
> > > + * MMU notifier UNMAP event. As mentioned above, ranges
> > > are tracked in
> > > + * a notifier's Red-Black tree.
> > > + * - Operations: Define the interface for driver-specific SVM
> > > operations such as
> > > + * allocation, page collection, migration,
> > > invalidations, and VRAM
> > > + * release.
> > > + *
> > > + * This layer provides interfaces for allocating, mapping,
> > > migrating, and
> > > + * releasing memory ranges between the CPU and GPU. It handles all
> > > core memory
> > > + * management interactions (DMA mapping, HMM, and migration) and
> > > provides
> > > + * driver-specific virtual functions (vfuncs). This infrastructure
> > > is sufficient
> > > + * to build the expected driver components for an SVM implementation
> > > as detailed
> > > + * below.
> > > + *
> > > + * Expected Driver Components:
> > > + * - GPU page fault handler: Used to create ranges and notifiers
> > > based on the
> > > + * fault address, optionally migrate the
> > > range to
> > > + * VRAM, and create GPU bindings.
> > > + * - Garbage collector: Used to destroy GPU bindings for ranges.
> > > Ranges are
> > > + * expected to be added to the garbage
> > > collector upon
> > > + * MMU_NOTIFY_UNMAP event.
> > > + */
> > > +
> > > +/**
> > > + * DOC: Locking
> > > + *
> > > + * GPU SVM handles locking for core MM interactions, i.e., it
> > > locks/unlocks the
> > > + * mmap lock as needed. Alternatively, if the driver prefers to
> > > handle the mmap
> > > + * lock itself, a 'locked' argument is provided to the functions
> > > that require
> > > + * the mmap lock. This option may be useful for drivers that need to
> > > call into
> > > + * GPU SVM while also holding a dma-resv lock, thus preventing
> > > locking
> > > + * inversions between the mmap and dma-resv locks.
> > > + *
> > > + * GPU SVM introduces a global notifier lock, which safeguards the
> > > notifier's
> > > + * range RB tree and list, as well as the range's DMA mappings and
> > > sequence
> > > + * number. GPU SVM manages all necessary locking and unlocking
> > > operations,
> > > + * except for the recheck of the range's sequence number
> > > + * (mmu_interval_read_retry) when the driver is committing GPU
> > > bindings. This
> > > + * lock corresponds to the 'driver->update' lock mentioned in the
> > > HMM
> > > + * documentation (TODO: Link). Future revisions may transition from
> > > a GPU SVM
> > > + * global lock to a per-notifier lock if finer-grained locking is
> > > deemed
> > > + * necessary.
> > > + *
> > > + * In addition to the locking mentioned above, the driver should
> > > implement a
> > > + * lock to safeguard core GPU SVM function calls that modify state,
> > > such as
> > > + * drm_gpusvm_range_find_or_insert and drm_gpusvm_range_remove.
> > > Alternatively,
> > > + * these core functions can be called within a single kernel thread,
> > > for
> > > + * instance, using an ordered work queue. This lock is denoted as
> > > + * 'driver_svm_lock' in code examples.
> > > + */
> > > +
> > > +/**
> > > + * DOC: Migrataion
> > > + *
> > > + * The migration support is quite simple, allowing migration between
> > > SRAM and
> > > + * VRAM at the range granularity. For example, GPU SVM currently
> > > does not
> > > + * support mixing SRAM and VRAM pages within a range. This means
> > > that upon GPU
> > > + * fault, the entire range can be migrated to VRAM, and upon CPU
> > > fault, the
> > > + * entire range is migrated to SRAM.
> > > + *
> > > + * The reasoning for only supporting range granularity is as
> > > follows: it
> > > + * simplifies the implementation, and range sizes are driver-defined
> > > and should
> > > + * be relatively small.
> > > + */
> > > +
> > > +/**
> > > + * DOC: Partial Unmapping of Ranges
> > > + *
> > > + * Partial unmapping of ranges (e.g., 1M out of 2M is unmapped by
> > > CPU resulting
> > > + * in MMU_NOTIFY_UNMAP event) presents several challenges, with the
> > > main one
> > > + * being that a subset of the range still has CPU and GPU mappings.
> > > If the
> > > + * backing store for the range is in VRAM, a subset of the backing
> > > store has
> > > + * references. One option would be to split the range and VRAM
> > > backing store,
> > > + * but the implementation for this would be quite complicated. Given
> > > that
> > > + * partial unmappings are rare and driver-defined range sizes are
> > > relatively
> > > + * small, GPU SVM does not support splitting of ranges.
> > > + *
> > > + * With no support for range splitting, upon partial unmapping of a
> > > range, the
> > > + * driver is expected to invalidate and destroy the entire range. If
> > > the range
> > > + * has VRAM as its backing, the driver is also expected to migrate
> > > any remaining
> > > + * pages back to SRAM.
> > > + */
> > > +
> > > +/**
> > > + * DOC: Examples
> > > + *
> > > + * This section provides two examples of how to build the expected
> > > driver
> > > + * components: the GPU page fault handler and the garbage collector.
> > > A third
> > > + * example demonstrates a sample invalidation driver vfunc.
> > > + *
> > > + * The generic code provided does not include logic for complex
> > > migration
> > > + * policies, optimized invalidations, or other potentially required
> > > driver
> > > + * locking (e.g., DMA-resv locks).
> > > + *
> > > + * 1) GPU page fault handler
> > > + *
> > > + * int driver_bind_range(struct drm_gpusvm *gpusvm, struct
> > > drm_gpusvm_range *range)
> > > + * {
> > > + * int err = 0;
> > > + *
> > > + * driver_alloc_and_setup_memory_for_bind(gpusvm,
> > > range);
> > > + *
> > > + * drm_gpusvm_notifier_lock(gpusvm);
> > > + * if (drm_gpusvm_range_pages_valid(range))
> > > + * driver_commit_bind(gpusvm, range);
> > > + * else
> > > + * err = -EAGAIN;
> > > + * drm_gpusvm_notifier_unlock(gpusvm);
> > > + *
> > > + * return err;
> > > + * }
> > > + *
> > > + * int driver_gpu_fault(struct drm_gpusvm *gpusvm, u64
> > > fault_addr,
> > > + * u64 gpuva_start, u64 gpuva_end)
> > > + * {
> > > + * struct drm_gpusvm_ctx ctx = {};
> > > + * int err;
> > > + *
> > > + * driver_svm_lock();
> > > + * retry:
> > > + * // Always process UNMAPs first so view of GPU SVM
> > > ranges is current
> > > + * driver_garbage_collector(gpusvm);
> > > + *
> > > + * range = drm_gpusvm_range_find_or_insert(gpusvm,
> > > fault_addr,
> > > + * gpuva_start,
> > > gpuva_end,
> > > + * &ctx);
> > > + * if (IS_ERR(range)) {
> > > + * err = PTR_ERR(range);
> > > + * goto unlock;
> > > + * }
> > > + *
> > > + * if (driver_migration_policy(range)) {
> > > + * bo = driver_alloc_bo();
> > > + * err = drm_gpusvm_migrate_to_vram(gpusvm,
> > > range, bo, &ctx);
> > > + * if (err) // CPU mappings may have
> > > changed
> > > + * goto retry;
> > > + * }
> > > + *
> > > + * err = drm_gpusvm_range_get_pages(gpusvm, range,
> > > &ctx);
> > > + * if (err == -EFAULT || err == -EPERM) // CPU
> > > mappings changed
> > > + * goto retry;
> > > + * else if (err)
> > > + * goto unlock;
> > > + *
> > > + * err = driver_bind_range(gpusvm, range);
> > > + * if (err == -EAGAIN) // CPU mappings changed
> > > + * goto retry
> > > + *
> > > + * unlock:
> > > + * driver_svm_unlock();
> > > + * return err;
> > > + * }
> > > + *
> > > + * 2) Garbage Collector.
> > > + *
> > > + * void __driver_garbage_collector(struct drm_gpusvm *gpusvm,
> > > + * struct drm_gpusvm_range
> > > *range)
> > > + * {
> > > + * struct drm_gpusvm_ctx ctx = {};
> > > + *
> > > + * assert_driver_svm_locked(gpusvm);
> > > + *
> > > + * // Partial unmap, migrate any remaining VRAM pages
> > > back to SRAM
> > > + * if (range->flags.partial_unmap)
> > > + * drm_gpusvm_migrate_to_sram(gpusvm, range,
> > > &ctx);
> > > + *
> > > + * driver_unbind_range(range);
> > > + * drm_gpusvm_range_remove(gpusvm, range);
> > > + * }
> > > + *
> > > + * void driver_garbage_collector(struct drm_gpusvm *gpusvm)
> > > + * {
> > > + * assert_driver_svm_locked(gpusvm);
> > > + *
> > > + * for_each_range_in_garbage_collector(gpusvm, range)
> > > + * __driver_garbage_collector(gpusvm, range);
> > > + * }
> > > + *
> > > + * 3) Invalidation driver vfunc.
> > > + *
> > > + * void driver_invalidation(struct drm_gpusvm *gpusvm,
> > > + * struct drm_gpusvm_notifier
> > > *notifier,
> > > + * const struct mmu_notifier_range
> > > *mmu_range)
> > > + * {
> > > + * struct drm_gpusvm_ctx ctx = { .in_notifier = true,
> > > };
> > > + * struct drm_gpusvm_range *range = NULL;
> > > + *
> > > + * driver_invalidate_device_tlb(gpusvm, mmu_range-
> > > >start, mmu_range->end);
> > > + *
> > > + * drm_gpusvm_for_each_range(range, notifier,
> > > mmu_range->start,
> > > + * mmu_range->end) {
> > > + * drm_gpusvm_range_unmap_pages(gpusvm, range,
> > > &ctx);
> > > + *
> > > + * if (mmu_range->event != MMU_NOTIFY_UNMAP)
> > > + * continue;
> > > + *
> > > + * drm_gpusvm_range_set_unmapped(range,
> > > mmu_range);
> > > + * driver_garbage_collector_add(gpusvm, range);
> > > + * }
> > > + * }
> > > + */
> > > +
> > > +#define DRM_GPUSVM_RANGE_START(_range) ((_range)->va.start)
> > > +#define DRM_GPUSVM_RANGE_END(_range) ((_range)->va.end - 1)
> > > +INTERVAL_TREE_DEFINE(struct drm_gpusvm_range, rb.node, u64,
> > > rb.__subtree_last,
> > > + DRM_GPUSVM_RANGE_START, DRM_GPUSVM_RANGE_END,
> > > + static __maybe_unused, range);
> > > +
> > > +#define DRM_GPUSVM_NOTIFIER_START(_notifier) ((_notifier)-
> > > >interval.start)
> > > +#define DRM_GPUSVM_NOTIFIER_END(_notifier) ((_notifier)-
> > > >interval.end - 1)
> > > +INTERVAL_TREE_DEFINE(struct drm_gpusvm_notifier, rb.node, u64,
> > > + rb.__subtree_last, DRM_GPUSVM_NOTIFIER_START,
> > > + DRM_GPUSVM_NOTIFIER_END, static __maybe_unused,
> > > notifier);
> > > +
> >
> > Since these trees span struct mm_struct address space which should fit
> > in an unsigned long, can we use the generic version (interval_tree.h)
> > rather than instantiating two new versions? I figure both contain
> > overlapping ranges so we can't use maple trees?
> >
>
> I can look into using a generic version but actually I don't think we
> allow overlapping so a maple tree might work here too. I'll likely stick
> a generic version in next rev but if the consensus is maple tree we can
> switch over to that fairly easy at any point in time as the tree
> interaction is completely encapsulated in DRM SVM layer.
>
> > > +/**
> > > + * npages_in_range() - Calculate the number of pages in a given
> > > range
> > > + * @start__: The start address of the range
> > > + * @end__: The end address of the range
> > > + *
> > > + * This macro calculates the number of pages in a given memory
> > > range,
> > > + * specified by the start and end addresses. It divides the
> > > difference
> > > + * between the end and start addresses by the page size (PAGE_SIZE)
> > > to
> > > + * determine the number of pages in the range.
> > > + *
> > > + * Return: The number of pages in the specified range.
> > > + */
> > > +#define npages_in_range(start__, end__) \
> > > + (((end__) - (start__)) >> PAGE_SHIFT)
> > > +
> > > +/**
> > > + * struct drm_gpusvm_zdd - GPU SVM zone device data
> > > + *
> > > + * @refcount: Reference count for the zdd
> > > + * @destroy_work: Work structure for asynchronous zdd destruction
> > > + * @range: Pointer to the GPU SVM range
> > > + * @vram_allocation: Driver-private pointer to the VRAM allocation
> > > + *
> > > + * This structure serves as a generic wrapper installed in
> > > + * page->zone_device_data. It provides infrastructure for looking up
> > > a range
> > > + * upon CPU page fault and asynchronously releasing VRAM once the
> > > CPU has no
> > > + * page references. Asynchronous release is useful because CPU page
> > > references
> > > + * can be dropped in IRQ contexts, while releasing VRAM likely
> > > requires sleeping
> > > + * locks.
> > > + */
> > > +struct drm_gpusvm_zdd {
> > > + struct kref refcount;
> > > + struct work_struct destroy_work;
> > > + struct drm_gpusvm_range *range;
> >
> > I still believe previous review comments are valid here, considering we
> > do have multiple drm_gpusvm per struct mm_struct, potentially all
> > mapping the above page.
> >
>
> Exactly which comments?
>
> If it related to the range pointer, that is going to be dropped. All
> virtual references from zdd will be dropped (i.e. no pointer to even a
> DRM SVM).
>
> > > + void *vram_allocation;
> >
> > NIT: Naming. The core is using device memory or devmem. Should we
> > follow.
> >
>
> I like devmem. Will change.
>
> > Also could we, rather than using av void * use an embeddable struct
> > with its own ops rather than using the gpusvm ops for this?
> >
>
> Can you give me code snippet example of what you think this should look
> like? Not opposed to this.
>
After reading your write up multi-device, yes I think a embeddable
struct with its own ops make sense.
I think the following ops should be moved to the embeddable struct:
vram_release
populate_vram_pfn
copy_to_vram
copy_to_sram
Also the local vram_attach, vram_detach, and vram_detached in the branch
I shared.
We likely want the device which owns the vram allocation in the embedded
struct too so that can be used for dma mapping when triggering
migration to a remote device or when a migrate_to_ram callback occurs.
Matt
> > > +};
> > > +
> > > +/**
> > > + * drm_gpusvm_zdd_destroy_work_func - Work function for destroying a
> > > zdd
> > > + * @w: Pointer to the work_struct
> > > + *
> > > + * This function releases VRAM, puts GPU SVM range, and frees zdd.
> > > + */
> > > +static void drm_gpusvm_zdd_destroy_work_func(struct work_struct *w)
> > > +{
> > > + struct drm_gpusvm_zdd *zdd =
> > > + container_of(w, struct drm_gpusvm_zdd,
> > > destroy_work);
> > > + struct drm_gpusvm_range *range = zdd->range;
> > > + struct drm_gpusvm *gpusvm = range->gpusvm;
> > > +
> > > + if (gpusvm->ops->vram_release && zdd->vram_allocation)
> > > + gpusvm->ops->vram_release(zdd->vram_allocation);
> > > + drm_gpusvm_range_put(range);
> > > + kfree(zdd);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_zdd_alloc - Allocate a zdd structure.
> > > + * @range: Pointer to the GPU SVM range.
> > > + *
> > > + * This function allocates and initializes a new zdd structure. It
> > > sets up the
> > > + * reference count, initializes the destroy work, and links the
> > > provided GPU SVM
> > > + * range.
> > > + *
> > > + * Returns:
> > > + * Pointer to the allocated zdd on success, ERR_PTR() on failure.
> > > + */
> > > +static struct drm_gpusvm_zdd *
> > > +drm_gpusvm_zdd_alloc(struct drm_gpusvm_range *range)
> > > +{
> > > + struct drm_gpusvm_zdd *zdd;
> > > +
> > > + zdd = kmalloc(sizeof(*zdd), GFP_KERNEL);
> > > + if (!zdd)
> > > + return NULL;
> > > +
> > > + kref_init(&zdd->refcount);
> > > + INIT_WORK(&zdd->destroy_work,
> > > drm_gpusvm_zdd_destroy_work_func);
> > > + zdd->range = drm_gpusvm_range_get(range);
> > > + zdd->vram_allocation = NULL;
> > > +
> > > + return zdd;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_zdd_get - Get a reference to a zdd structure.
> > > + * @zdd: Pointer to the zdd structure.
> > > + *
> > > + * This function increments the reference count of the provided zdd
> > > structure.
> > > + *
> > > + * Returns: Pointer to the zdd structure.
> > > + */
> > > +static struct drm_gpusvm_zdd *drm_gpusvm_zdd_get(struct
> > > drm_gpusvm_zdd *zdd)
> > > +{
> > > + kref_get(&zdd->refcount);
> > > + return zdd;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_zdd_destroy - Destroy a zdd structure.
> > > + * @ref: Pointer to the reference count structure.
> > > + *
> > > + * This function queues the destroy_work of the zdd for asynchronous
> > > destruction.
> > > + */
> > > +static void drm_gpusvm_zdd_destroy(struct kref *ref)
> > > +{
> > > + struct drm_gpusvm_zdd *zdd =
> > > + container_of(ref, struct drm_gpusvm_zdd, refcount);
> > > + struct drm_gpusvm *gpusvm = zdd->range->gpusvm;
> > > +
> > > + queue_work(gpusvm->zdd_wq, &zdd->destroy_work);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_zdd_put - Put a zdd reference.
> > > + * @zdd: Pointer to the zdd structure.
> > > + *
> > > + * This function decrements the reference count of the provided zdd
> > > structure
> > > + * and schedules its destruction if the count drops to zero.
> > > + */
> > > +static void drm_gpusvm_zdd_put(struct drm_gpusvm_zdd *zdd)
> > > +{
> > > + kref_put(&zdd->refcount, drm_gpusvm_zdd_destroy);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_find - Find GPU SVM range from GPU SVM notifier
> > > + * @notifier: Pointer to the GPU SVM notifier structure.
> > > + * @start: Start address of the range
> > > + * @end: End address of the range
> > > + *
> > > + * Return: A pointer to the drm_gpusvm_range if found or NULL
> > > + */
> > > +struct drm_gpusvm_range *
> > > +drm_gpusvm_range_find(struct drm_gpusvm_notifier *notifier, u64
> > > start, u64 end)
> > > +{
> > > + return range_iter_first(¬ifier->root, start, end - 1);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_for_each_range_safe - Safely iterate over GPU SVM
> > > ranges in a notifier
> > > + * @range__: Iterator variable for the ranges
> > > + * @next__: Iterator variable for the ranges temporay storage
> > > + * @notifier__: Pointer to the GPU SVM notifier
> > > + * @start__: Start address of the range
> > > + * @end__: End address of the range
> > > + *
> > > + * This macro is used to iterate over GPU SVM ranges in a notifier
> > > while
> > > + * removing ranges from it.
> > > + */
> > > +#define drm_gpusvm_for_each_range_safe(range__, next__, notifier__,
> > > start__, end__) \
> > > + for ((range__) = drm_gpusvm_range_find((notifier__),
> > > (start__), (end__)), \
> > > + (next__) =
> > > __drm_gpusvm_range_next(range__); \
> > > + (range__) && (range__->va.start <
> > > (end__)); \
> > > + (range__) = (next__), (next__) =
> > > __drm_gpusvm_range_next(range__))
> > > +
> > > +/**
> > > + * __drm_gpusvm_notifier_next - get the next drm_gpusvm_notifier in
> > > the list
> > > + * @notifier: a pointer to the current drm_gpusvm_notifier
> > > + *
> > > + * Return: A pointer to the next drm_gpusvm_notifier if available,
> > > or NULL if
> > > + * the current notifier is the last one or if the input
> > > notifier is
> > > + * NULL.
> > > + */
> > > +static struct drm_gpusvm_notifier *
> > > +__drm_gpusvm_notifier_next(struct drm_gpusvm_notifier *notifier)
> > > +{
> > > + if (notifier && !list_is_last(¬ifier->rb.entry,
> > > + ¬ifier->gpusvm-
> > > >notifier_list))
> > > + return list_next_entry(notifier, rb.entry);
> > > +
> > > + return NULL;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_for_each_notifier - Iterate over GPU SVM notifiers in
> > > a gpusvm
> > > + * @notifier__: Iterator variable for the notifiers
> > > + * @notifier__: Pointer to the GPU SVM notifier
> > > + * @start__: Start address of the notifier
> > > + * @end__: End address of the notifier
> > > + *
> > > + * This macro is used to iterate over GPU SVM notifiers in a gpusvm.
> > > + */
> > > +#define drm_gpusvm_for_each_notifier(notifier__, gpusvm__, start__,
> > > end__) \
> > > + for ((notifier__) = notifier_iter_first(&(gpusvm__)->root,
> > > (start__), (end__) - 1); \
> > > + (notifier__) && (notifier__->interval.start <
> > > (end__)); \
> > > + (notifier__) = __drm_gpusvm_notifier_next(notifier__))
> > > +
> > > +/**
> > > + * drm_gpusvm_for_each_notifier_safe - Safely iterate over GPU SVM
> > > notifiers in a gpusvm
> > > + * @notifier__: Iterator variable for the notifiers
> > > + * @next__: Iterator variable for the notifiers temporay storage
> > > + * @notifier__: Pointer to the GPU SVM notifier
> > > + * @start__: Start address of the notifier
> > > + * @end__: End address of the notifier
> > > + *
> > > + * This macro is used to iterate over GPU SVM notifiers in a gpusvm
> > > while
> > > + * removing notifiers from it.
> > > + */
> > > +#define drm_gpusvm_for_each_notifier_safe(notifier__, next__,
> > > gpusvm__, start__, end__) \
> > > + for ((notifier__) = notifier_iter_first(&(gpusvm__)->root,
> > > (start__), (end__) - 1), \
> > > + (next__) =
> > > __drm_gpusvm_notifier_next(notifier__); \
> > > + (notifier__) && (notifier__->interval.start <
> > > (end__)); \
> > > + (notifier__) = (next__), (next__) =
> > > __drm_gpusvm_notifier_next(notifier__))
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_invalidate - Invalidate a GPU SVM notifier.
> > > + * @mni: Pointer to the mmu_interval_notifier structure.
> > > + * @mmu_range: Pointer to the mmu_notifier_range structure.
> > > + * @cur_seq: Current sequence number.
> > > + *
> > > + * This function serves as a generic MMU notifier for GPU SVM. It
> > > sets the MMU
> > > + * notifier sequence number and calls the driver invalidate vfunc
> > > under
> > > + * gpusvm->notifier_lock.
> > > + *
> > > + * Returns:
> > > + * true if the operation succeeds, false otherwise.
> > > + */
> > > +static bool
> > > +drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier *mni,
> > > + const struct mmu_notifier_range
> > > *mmu_range,
> > > + unsigned long cur_seq)
> > > +{
> > > + struct drm_gpusvm_notifier *notifier =
> > > + container_of(mni, typeof(*notifier), notifier);
> > > + struct drm_gpusvm *gpusvm = notifier->gpusvm;
> > > +
> > > + if (!mmu_notifier_range_blockable(mmu_range))
> > > + return false;
> > > +
> > > + down_write(&gpusvm->notifier_lock);
> > > + mmu_interval_set_seq(mni, cur_seq);
> > > + gpusvm->ops->invalidate(gpusvm, notifier, mmu_range);
> > > + up_write(&gpusvm->notifier_lock);
> > > +
> > > + return true;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_ops - MMU interval notifier operations for
> > > GPU SVM
> > > + */
> > > +static const struct mmu_interval_notifier_ops
> > > drm_gpusvm_notifier_ops = {
> > > + .invalidate = drm_gpusvm_notifier_invalidate,
> > > +};
> > > +
> > > +/**
> > > + * drm_gpusvm_init - Initialize the GPU SVM.
> > > + * @gpusvm: Pointer to the GPU SVM structure.
> > > + * @name: Name of the GPU SVM.
> > > + * @drm: Pointer to the DRM device structure.
> > > + * @mm: Pointer to the mm_struct for the address space.
> > > + * @device_private_page_owner: Device private pages owner.
> > > + * @mm_start: Start address of GPU SVM.
> > > + * @mm_range: Range of the GPU SVM.
> > > + * @notifier_size: Size of individual notifiers.
> > > + * @ops: Pointer to the operations structure for GPU SVM.
> > > + * @chunk_sizes: Pointer to the array of chunk sizes used in range
> > > allocation.
> > > + * Entries should be powers of 2 in descending order
> > > with last
> > > + * entry being SZ_4K.
> > > + * @num_chunks: Number of chunks.
> > > + *
> > > + * This function initializes the GPU SVM.
> > > + *
> > > + * Returns:
> > > + * 0 on success, a negative error code on failure.
> > > + */
> > > +int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
> > > + const char *name, struct drm_device *drm,
> > > + struct mm_struct *mm, void
> > > *device_private_page_owner,
> > > + u64 mm_start, u64 mm_range, u64 notifier_size,
> > > + const struct drm_gpusvm_ops *ops,
> > > + const u64 *chunk_sizes, int num_chunks)
> > > +{
> > > + if (!ops->invalidate || !num_chunks)
> > > + return -EINVAL;
> > > +
> > > + gpusvm->name = name;
> > > + gpusvm->drm = drm;
> > > + gpusvm->mm = mm;
> > > + gpusvm->device_private_page_owner =
> > > device_private_page_owner;
> > > + gpusvm->mm_start = mm_start;
> > > + gpusvm->mm_range = mm_range;
> > > + gpusvm->notifier_size = notifier_size;
> > > + gpusvm->ops = ops;
> > > + gpusvm->chunk_sizes = chunk_sizes;
> > > + gpusvm->num_chunks = num_chunks;
> > > + gpusvm->zdd_wq = system_wq;
> > > +
> > > + mmgrab(mm);
> > > + gpusvm->root = RB_ROOT_CACHED;
> > > + INIT_LIST_HEAD(&gpusvm->notifier_list);
> > > +
> > > + init_rwsem(&gpusvm->notifier_lock);
> > > +
> > > + fs_reclaim_acquire(GFP_KERNEL);
> > > + might_lock(&gpusvm->notifier_lock);
> > > + fs_reclaim_release(GFP_KERNEL);
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_find - Find GPU SVM notifier
> > > + * @gpusvm__: Pointer to the GPU SVM structure
> > > + * @fault_addr__: Fault address
> > > + *
> > > + * This macro finds the GPU SVM notifier associated with the fault
> > > address.
> > > + *
> > > + * Returns:
> > > + * Pointer to the GPU SVM notifier on success, NULL otherwise.
> > > + */
> > > +#define drm_gpusvm_notifier_find(gpusvm__, fault_addr__) \
> > > + notifier_iter_first(&(gpusvm__)->root, (fault_addr__), \
> > > + (fault_addr__ + 1))
> > > +
> > > +/**
> > > + * to_drm_gpusvm_notifier - retrieve the container struct for a
> > > given rbtree node
> > > + * @node__: a pointer to the rbtree node embedded within a
> > > drm_gpusvm_notifier struct
> > > + *
> > > + * Return: A pointer to the containing drm_gpusvm_notifier
> > > structure.
> > > + */
> > > +#define to_drm_gpusvm_notifier(__node) \
> > > + container_of((__node), struct drm_gpusvm_notifier, rb.node)
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_insert - Insert GPU SVM notifier
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > + *
> > > + * This function inserts the GPU SVM notifier into the GPU SVM RB
> > > tree and list.
> > > + */
> > > +static void drm_gpusvm_notifier_insert(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_notifier
> > > *notifier)
> > > +{
> > > + struct rb_node *node;
> > > + struct list_head *head;
> > > +
> > > + notifier_insert(notifier, &gpusvm->root);
> > > +
> > > + node = rb_prev(¬ifier->rb.node);
> > > + if (node)
> > > + head = &(to_drm_gpusvm_notifier(node))->rb.entry;
> > > + else
> > > + head = &gpusvm->notifier_list;
> > > +
> > > + list_add(¬ifier->rb.entry, head);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_remove - Remove GPU SVM notifier
> > > + * @gpusvm__: Pointer to the GPU SVM tructure
> > > + * @notifier__: Pointer to the GPU SVM notifier structure
> > > + *
> > > + * This macro removes the GPU SVM notifier from the GPU SVM RB tree
> > > and list.
> > > + */
> > > +#define drm_gpusvm_notifier_remove(gpusvm__, notifier__) \
> > > + notifier_remove((notifier__), &(gpusvm__)->root); \
> > > + list_del(&(notifier__)->rb.entry)
> > > +
> > > +/**
> > > + * drm_gpusvm_fini - Finalize the GPU SVM.
> > > + * @gpusvm: Pointer to the GPU SVM structure.
> > > + *
> > > + * This function finalizes the GPU SVM by cleaning up any remaining
> > > ranges and
> > > + * notifiers, and dropping a reference to struct MM.
> > > + */
> > > +void drm_gpusvm_fini(struct drm_gpusvm *gpusvm)
> > > +{
> > > + struct drm_gpusvm_notifier *notifier, *next;
> > > +
> > > + drm_gpusvm_for_each_notifier_safe(notifier, next, gpusvm, 0,
> > > LONG_MAX) {
> > > + struct drm_gpusvm_range *range, *__next;
> > > +
> > > + /*
> > > + * Remove notifier first to avoid racing with any
> > > invalidation
> > > + */
> > > + mmu_interval_notifier_remove(¬ifier->notifier);
> > > + notifier->flags.removed = true;
> > > +
> > > + drm_gpusvm_for_each_range_safe(range, __next,
> > > notifier, 0,
> > > + LONG_MAX)
> > > + drm_gpusvm_range_remove(gpusvm, range);
> > > + }
> > > +
> > > + mmdrop(gpusvm->mm);
> > > + WARN_ON(!RB_EMPTY_ROOT(&gpusvm->root.rb_root));
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_alloc - Allocate GPU SVM notifier
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @fault_addr: Fault address
> > > + *
> > > + * This function allocates and initializes the GPU SVM notifier
> > > structure.
> > > + *
> > > + * Returns:
> > > + * Pointer to the allocated GPU SVM notifier on success, ERR_PTR()
> > > on failure.
> > > + */
> > > +static struct drm_gpusvm_notifier *
> > > +drm_gpusvm_notifier_alloc(struct drm_gpusvm *gpusvm, u64 fault_addr)
> > > +{
> > > + struct drm_gpusvm_notifier *notifier;
> > > +
> > > + if (gpusvm->ops->notifier_alloc)
> > > + notifier = gpusvm->ops->notifier_alloc();
> > > + else
> > > + notifier = kzalloc(sizeof(*notifier), GFP_KERNEL);
> > > +
> > > + if (!notifier)
> > > + return ERR_PTR(-ENOMEM);
> > > +
> > > + notifier->gpusvm = gpusvm;
> > > + notifier->interval.start = ALIGN_DOWN(fault_addr, gpusvm-
> > > >notifier_size);
> > > + notifier->interval.end = ALIGN(fault_addr + 1, gpusvm-
> > > >notifier_size);
> > > + INIT_LIST_HEAD(¬ifier->rb.entry);
> > > + notifier->root = RB_ROOT_CACHED;
> > > + INIT_LIST_HEAD(¬ifier->range_list);
> > > +
> > > + return notifier;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_free - Free GPU SVM notifier
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > + *
> > > + * This function frees the GPU SVM notifier structure.
> > > + */
> > > +static void drm_gpusvm_notifier_free(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_notifier
> > > *notifier)
> > > +{
> > > + WARN_ON(!RB_EMPTY_ROOT(¬ifier->root.rb_root));
> > > +
> > > + if (gpusvm->ops->notifier_free)
> > > + gpusvm->ops->notifier_free(notifier);
> > > + else
> > > + kfree(notifier);
> > > +}
> > > +
> > > +/**
> > > + * to_drm_gpusvm_range - retrieve the container struct for a given
> > > rbtree node
> > > + * @node__: a pointer to the rbtree node embedded within a
> > > drm_gpusvm_range struct
> > > + *
> > > + * Return: A pointer to the containing drm_gpusvm_range structure.
> > > + */
> > > +#define to_drm_gpusvm_range(node__) \
> > > + container_of((node__), struct drm_gpusvm_range, rb.node)
> > > +
> > > +/**
> > > + * drm_gpusvm_range_insert - Insert GPU SVM range
> > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + *
> > > + * This function inserts the GPU SVM range into the notifier RB tree
> > > and list.
> > > + */
> > > +static void drm_gpusvm_range_insert(struct drm_gpusvm_notifier
> > > *notifier,
> > > + struct drm_gpusvm_range *range)
> > > +{
> > > + struct rb_node *node;
> > > + struct list_head *head;
> > > +
> > > + drm_gpusvm_notifier_lock(notifier->gpusvm);
> > > + range_insert(range, ¬ifier->root);
> > > +
> > > + node = rb_prev(&range->rb.node);
> > > + if (node)
> > > + head = &(to_drm_gpusvm_range(node))->rb.entry;
> > > + else
> > > + head = ¬ifier->range_list;
> > > +
> > > + list_add(&range->rb.entry, head);
> > > + drm_gpusvm_notifier_unlock(notifier->gpusvm);
> > > +}
> > > +
> > > +/**
> > > + * __drm_gpusvm_range_remove - Remove GPU SVM range
> > > + * @notifier__: Pointer to the GPU SVM notifier structure
> > > + * @range__: Pointer to the GPU SVM range structure
> > > + *
> > > + * This macro removes the GPU SVM range from the notifier RB tree
> > > and list.
> > > + */
> > > +#define __drm_gpusvm_range_remove(notifier__, range__) \
> > > + range_remove((range__), &(notifier__)->root); \
> > > + list_del(&(range__)->rb.entry)
> > > +
> > > +/**
> > > + * drm_gpusvm_range_alloc - Allocate GPU SVM range
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > + * @fault_addr: Fault address
> > > + * @chunk_size: Chunk size
> > > + * @migrate_vram: Flag indicating whether to migrate VRAM
> > > + *
> > > + * This function allocates and initializes the GPU SVM range
> > > structure.
> > > + *
> > > + * Returns:
> > > + * Pointer to the allocated GPU SVM range on success, ERR_PTR() on
> > > failure.
> > > + */
> > > +static struct drm_gpusvm_range *
> > > +drm_gpusvm_range_alloc(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_notifier *notifier,
> > > + u64 fault_addr, u64 chunk_size, bool
> > > migrate_vram)
> > > +{
> > > + struct drm_gpusvm_range *range;
> > > +
> > > + if (gpusvm->ops->range_alloc)
> > > + range = gpusvm->ops->range_alloc(gpusvm);
> > > + else
> > > + range = kzalloc(sizeof(*range), GFP_KERNEL);
> > > +
> > > + if (!range)
> > > + return ERR_PTR(-ENOMEM);
> > > +
> > > + kref_init(&range->refcount);
> > > + range->gpusvm = gpusvm;
> > > + range->notifier = notifier;
> > > + range->va.start = ALIGN_DOWN(fault_addr, chunk_size);
> > > + range->va.end = ALIGN(fault_addr + 1, chunk_size);
> > > + INIT_LIST_HEAD(&range->rb.entry);
> > > + range->notifier_seq = LONG_MAX;
> > > + range->flags.migrate_vram = migrate_vram ? 1 : 0;
> > > +
> > > + return range;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_check_pages - Check pages
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > + * @start: Start address
> > > + * @end: End address
> > > + *
> > > + * Check if pages between start and end have been faulted in on the
> > > CPU. Use to
> > > + * prevent migration of pages without CPU backing store.
> > > + *
> > > + * Returns:
> > > + * True if pages have been faulted into CPU, False otherwise
> > > + */
> > > +static bool drm_gpusvm_check_pages(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_notifier
> > > *notifier,
> > > + u64 start, u64 end)
> > > +{
> > > + struct hmm_range hmm_range = {
> > > + .default_flags = 0,
> > > + .notifier = ¬ifier->notifier,
> > > + .start = start,
> > > + .end = end,
> > > + .dev_private_owner = gpusvm-
> > > >device_private_page_owner,
> > > + };
> > > + unsigned long timeout =
> > > + jiffies +
> > > msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > > + unsigned long *pfns;
> > > + unsigned long npages = npages_in_range(start, end);
> > > + int err, i;
> > > +
> > > + mmap_assert_locked(gpusvm->mm);
> > > +
> > > + pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
> > > + if (!pfns)
> > > + return false;
> > > +
> > > + hmm_range.notifier_seq = mmu_interval_read_begin(¬ifier-
> > > >notifier);
> > > + hmm_range.hmm_pfns = pfns;
> > > +
> > > + while (true) {
> > > + err = hmm_range_fault(&hmm_range);
> > > + if (err == -EBUSY) {
> > > + if (time_after(jiffies, timeout))
> > > + break;
> > > +
> > > + hmm_range.notifier_seq =
> > > mmu_interval_read_begin(¬ifier->notifier);
> > > + continue;
> > > + }
> > > + break;
> > > + }
> > > + if (err)
> > > + goto err_free;
> > > +
> > > + for (i = 0; i < npages; ++i) {
> > > + if (!(pfns[i] & HMM_PFN_VALID)) {
> > > + err = -EFAULT;
> > > + goto err_free;
> > > + }
> > > + }
> > > +
> > > +err_free:
> > > + kvfree(pfns);
> > > + return err ? false : true;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_chunk_size - Determine chunk size for GPU SVM
> > > range
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @notifier: Pointer to the GPU SVM notifier structure
> > > + * @vas: Pointer to the virtual memory area structure
> > > + * @fault_addr: Fault address
> > > + * @gpuva_start: Start address of GPUVA which mirrors CPU
> > > + * @gpuva_end: End address of GPUVA which mirrors CPU
> > > + * @check_pages: Flag indicating whether to check pages
> > > + *
> > > + * This function determines the chunk size for the GPU SVM range
> > > based on the
> > > + * fault address, GPU SVM chunk sizes, existing GPU SVM ranges, and
> > > the virtual
> > > + * memory area boundaries.
> > > + *
> > > + * Returns:
> > > + * Chunk size on success, LONG_MAX on failure.
> > > + */
> > > +static u64 drm_gpusvm_range_chunk_size(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_notifier
> > > *notifier,
> > > + struct vm_area_struct *vas,
> > > + u64 fault_addr, u64
> > > gpuva_start,
> > > + u64 gpuva_end, bool
> > > check_pages)
> > > +{
> > > + u64 start, end;
> > > + int i = 0;
> > > +
> > > +retry:
> > > + for (; i < gpusvm->num_chunks; ++i) {
> > > + start = ALIGN_DOWN(fault_addr, gpusvm-
> > > >chunk_sizes[i]);
> > > + end = ALIGN(fault_addr + 1, gpusvm->chunk_sizes[i]);
> > > +
> > > + if (start >= vas->vm_start && end <= vas->vm_end &&
> > > + start >= notifier->interval.start &&
> > > + end <= notifier->interval.end &&
> > > + start >= gpuva_start && end <= gpuva_end)
> > > + break;
> > > + }
> > > +
> > > + if (i == gpusvm->num_chunks)
> > > + return LONG_MAX;
> > > +
> > > + /*
> > > + * If allocation more than page, ensure not to overlap with
> > > existing
> > > + * ranges.
> > > + */
> > > + if (end - start != SZ_4K) {
> > > + struct drm_gpusvm_range *range;
> > > +
> > > + range = drm_gpusvm_range_find(notifier, start, end);
> > > + if (range) {
> > > + ++i;
> > > + goto retry;
> > > + }
> > > +
> > > + /*
> > > + * XXX: Only create range on pages CPU has faulted
> > > in. Without
> > > + * this check, or prefault, on BMG
> > > 'xe_exec_system_allocator --r
> > > + * process-many-malloc' fails. In the failure case,
> > > each process
> > > + * mallocs 16k but the CPU VMA is ~128k which
> > > results in 64k SVM
> > > + * ranges. When migrating the SVM ranges, some
> > > processes fail in
> > > + * drm_gpusvm_migrate_to_vram with 'migrate.cpages
> > > != npages'
> > > + * and then upon drm_gpusvm_range_get_pages device
> > > pages from
> > > + * other processes are collected + faulted in which
> > > creates all
> > > + * sorts of problems. Unsure exactly how this
> > > happening, also
> > > + * problem goes away if 'xe_exec_system_allocator --
> > > r
> > > + * process-many-malloc' mallocs at least 64k at a
> > > time.
> > > + */
> > > + if (check_pages &&
> > > + !drm_gpusvm_check_pages(gpusvm, notifier, start,
> > > end)) {
> > > + ++i;
> > > + goto retry;
> > > + }
> > > + }
> > > +
> > > + return end - start;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_find_or_insert - Find or insert GPU SVM range
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @fault_addr: Fault address
> > > + * @gpuva_start: Start address of GPUVA which mirrors CPU
> > > + * @gpuva_end: End address of GPUVA which mirrors CPU
> > > + * @ctx: GPU SVM context
> > > + *
> > > + * This function finds or inserts a newly allocated a GPU SVM range
> > > based on the
> > > + * fault address. Caller must hold a lock to protect range lookup
> > > and insertion.
> > > + *
> > > + * Returns:
> > > + * Pointer to the GPU SVM range on success, ERR_PTR() on failure.
> > > + */
> > > +struct drm_gpusvm_range *
> > > +drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm, u64
> > > fault_addr,
> > > + u64 gpuva_start, u64 gpuva_end,
> > > + const struct drm_gpusvm_ctx *ctx)
> > > +{
> > > + struct drm_gpusvm_notifier *notifier;
> > > + struct drm_gpusvm_range *range;
> > > + struct mm_struct *mm = gpusvm->mm;
> > > + struct vm_area_struct *vas;
> > > + bool notifier_alloc = false;
> > > + u64 chunk_size;
> > > + int err;
> > > + bool migrate_vram;
> > > +
> > > + if (fault_addr < gpusvm->mm_start ||
> > > + fault_addr > gpusvm->mm_start + gpusvm->mm_range) {
> > > + err = -EINVAL;
> > > + goto err_out;
> > > + }
> > > +
> > > + if (!ctx->mmap_locked) {
> > > + if (!mmget_not_zero(mm)) {
> > > + err = -EFAULT;
> > > + goto err_out;
> > > + }
> > > + mmap_write_lock(mm);
> > > + }
> > > +
> > > + mmap_assert_write_locked(mm);
> > > +
> > > + notifier = drm_gpusvm_notifier_find(gpusvm, fault_addr);
> > > + if (!notifier) {
> > > + notifier = drm_gpusvm_notifier_alloc(gpusvm,
> > > fault_addr);
> > > + if (IS_ERR(notifier)) {
> > > + err = PTR_ERR(notifier);
> > > + goto err_mmunlock;
> > > + }
> > > + notifier_alloc = true;
> > > + err = mmu_interval_notifier_insert_locked(¬ifier-
> > > >notifier,
> > > + mm,
> > > notifier->interval.start,
> > > + notifier-
> > > >interval.end -
> > > + notifier-
> > > >interval.start,
> > > +
> > > &drm_gpusvm_notifier_ops);
> > > + if (err)
> > > + goto err_notifier;
> > > + }
> > > +
> > > + vas = vma_lookup(mm, fault_addr);
> > > + if (!vas) {
> > > + err = -ENOENT;
> > > + goto err_notifier_remove;
> > > + }
> > > +
> > > + if (!ctx->read_only && !(vas->vm_flags & VM_WRITE)) {
> > > + err = -EPERM;
> > > + goto err_notifier_remove;
> > > + }
> > > +
> > > + range = drm_gpusvm_range_find(notifier, fault_addr,
> > > fault_addr + 1);
> > > + if (range)
> > > + goto out_mmunlock;
> > > + /*
> > > + * XXX: Short-circuiting migration based on migrate_vma_*
> > > current
> > > + * limitations. If/when migrate_vma_* add more support, this
> > > logic will
> > > + * have to change.
> > > + */
> > > + migrate_vram = ctx->vram_possible &&
> > > + vma_is_anonymous(vas) && !is_vm_hugetlb_page(vas);
> > > +
> > > + chunk_size = drm_gpusvm_range_chunk_size(gpusvm, notifier,
> > > vas,
> > > + fault_addr,
> > > gpuva_start,
> > > + gpuva_end,
> > > migrate_vram &&
> > > + !ctx->prefault);
> > > + if (chunk_size == LONG_MAX) {
> > > + err = -EINVAL;
> > > + goto err_notifier_remove;
> > > + }
> > > +
> > > + range = drm_gpusvm_range_alloc(gpusvm, notifier, fault_addr,
> > > chunk_size,
> > > + migrate_vram);
> > > + if (IS_ERR(range)) {
> > > + err = PTR_ERR(range);
> > > + goto err_notifier_remove;
> > > + }
> > > +
> > > + drm_gpusvm_range_insert(notifier, range);
> > > + if (notifier_alloc)
> > > + drm_gpusvm_notifier_insert(gpusvm, notifier);
> > > +
> > > + if (ctx->prefault) {
> > > + struct drm_gpusvm_ctx __ctx = *ctx;
> > > +
> > > + __ctx.mmap_locked = true;
> > > + err = drm_gpusvm_range_get_pages(gpusvm, range,
> > > &__ctx);
> > > + if (err)
> > > + goto err_range_remove;
> > > + }
> > > +
> > > +out_mmunlock:
> > > + if (!ctx->mmap_locked) {
> > > + mmap_write_unlock(mm);
> > > + mmput(mm);
> > > + }
> > > +
> > > + return range;
> > > +
> > > +err_range_remove:
> > > + __drm_gpusvm_range_remove(notifier, range);
> > > +err_notifier_remove:
> > > + if (notifier_alloc)
> > > + mmu_interval_notifier_remove(¬ifier->notifier);
> > > +err_notifier:
> > > + if (notifier_alloc)
> > > + drm_gpusvm_notifier_free(gpusvm, notifier);
> > > +err_mmunlock:
> > > + if (!ctx->mmap_locked) {
> > > + mmap_write_unlock(mm);
> > > + mmput(mm);
> > > + }
> > > +err_out:
> > > + return ERR_PTR(err);
> > > +}
> > > +
> > > +/**
> > > + * for_each_dma_page - iterate over pages in a DMA regio`n
> > > + * @i__: the current page index in the iteration
> > > + * @j__: the current page index, log order, in the iteration
> > > + * @npages__: the total number of pages in the DMA region
> > > + * @order__: the order of the pages in the DMA region
> > > + *
> > > + * This macro iterates over each page in a DMA region. The DMA
> > > region
> > > + * is assumed to be composed of 2^@order__ pages, and the macro will
> > > + * step through the region one block of 2^@order__ pages at a time.
> > > + */
> > > +#define for_each_dma_page(i__, j__, npages__, order__) \
> > > + for ((i__) = 0, (j__) = 0; (i__) < (npages__); \
> > > + (j__)++, (i__) += 0x1 << (order__))
> > > +
> > > +/**
> > > + * __drm_gpusvm_range_unmap_pages - Unmap pages associated with a
> > > GPU SVM range (internal)
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + *
> > > + * This function unmap pages associated with a GPU SVM range.
> > > Assumes and
> > > + * asserts correct locking is in place when called.
> > > + */
> > > +static void __drm_gpusvm_range_unmap_pages(struct drm_gpusvm
> > > *gpusvm,
> > > + struct drm_gpusvm_range
> > > *range)
> > > +{
> > > + lockdep_assert_held(&gpusvm->notifier_lock);
> > > +
> > > + if (range->pages) {
> > > + unsigned long i, j, npages = npages_in_range(range-
> > > >va.start,
> > > + range-
> > > >va.end);
> > > +
> > > + if (range->flags.has_dma_mapping) {
> > > + for_each_dma_page(i, j, npages, range-
> > > >order)
> > > + dma_unmap_page(gpusvm->drm->dev,
> > > + range->dma_addr[j],
> > > + PAGE_SIZE << range-
> > > >order,
> > > + DMA_BIDIRECTIONAL);
> > > + }
> > > +
> > > + range->flags.has_vram_pages = false;
> > > + range->flags.has_dma_mapping = false;
> > > + }
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_free_pages - Free pages associated with a GPU
> > > SVM range
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + *
> > > + * This function free pages associated with a GPU SVM range.
> > > + */
> > > +static void drm_gpusvm_range_free_pages(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range
> > > *range)
> > > +{
> > > + lockdep_assert_held(&gpusvm->notifier_lock);
> > > +
> > > + if (range->pages) {
> > > + if (range->flags.kfree_mapping) {
> > > + kfree(range->dma_addr);
> > > + range->flags.kfree_mapping = false;
> > > + range->pages = NULL;
> > > + } else {
> > > + kvfree(range->pages);
> > > + range->pages = NULL;
> > > + }
> > > + }
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_remove - Remove GPU SVM range
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range to be removed
> > > + *
> > > + * This function removes the specified GPU SVM range and also
> > > removes the parent
> > > + * GPU SVM notifier if no more ranges remain in the notifier. The
> > > caller must
> > > + * hold a lock to protect range and notifier removal.
> > > + */
> > > +void drm_gpusvm_range_remove(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range)
> > > +{
> > > + struct drm_gpusvm_notifier *notifier;
> > > +
> > > + notifier = drm_gpusvm_notifier_find(gpusvm, range-
> > > >va.start);
> > > + if (WARN_ON_ONCE(!notifier))
> > > + return;
> > > +
> > > + drm_gpusvm_notifier_lock(gpusvm);
> > > + __drm_gpusvm_range_unmap_pages(gpusvm, range);
> > > + drm_gpusvm_range_free_pages(gpusvm, range);
> > > + __drm_gpusvm_range_remove(notifier, range);
> > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > +
> > > + drm_gpusvm_range_put(range);
> > > +
> > > + if (RB_EMPTY_ROOT(¬ifier->root.rb_root)) {
> > > + if (!notifier->flags.removed)
> > > + mmu_interval_notifier_remove(¬ifier-
> > > >notifier);
> > > + drm_gpusvm_notifier_remove(gpusvm, notifier);
> > > + drm_gpusvm_notifier_free(gpusvm, notifier);
> > > + }
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_get - Get a reference to GPU SVM range
> > > + * @range: Pointer to the GPU SVM range
> > > + *
> > > + * This function increments the reference count of the specified GPU
> > > SVM range.
> > > + *
> > > + * Returns:
> > > + * Pointer to the GPU SVM range.
> > > + */
> > > +struct drm_gpusvm_range *
> > > +drm_gpusvm_range_get(struct drm_gpusvm_range *range)
> > > +{
> > > + kref_get(&range->refcount);
> > > +
> > > + return range;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_destroy - Destroy GPU SVM range
> > > + * @refcount: Pointer to the reference counter embedded in the GPU
> > > SVM range
> > > + *
> > > + * This function destroys the specified GPU SVM range when its
> > > reference count
> > > + * reaches zero. If a custom range-free function is provided, it is
> > > invoked to
> > > + * free the range; otherwise, the range is deallocated using
> > > kfree().
> > > + */
> > > +static void drm_gpusvm_range_destroy(struct kref *refcount)
> > > +{
> > > + struct drm_gpusvm_range *range =
> > > + container_of(refcount, struct drm_gpusvm_range,
> > > refcount);
> > > + struct drm_gpusvm *gpusvm = range->gpusvm;
> > > +
> > > + if (gpusvm->ops->range_free)
> > > + gpusvm->ops->range_free(range);
> > > + else
> > > + kfree(range);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_put - Put a reference to GPU SVM range
> > > + * @range: Pointer to the GPU SVM range
> > > + *
> > > + * This function decrements the reference count of the specified GPU
> > > SVM range
> > > + * and frees it when the count reaches zero.
> > > + */
> > > +void drm_gpusvm_range_put(struct drm_gpusvm_range *range)
> > > +{
> > > + kref_put(&range->refcount, drm_gpusvm_range_destroy);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_pages_valid - GPU SVM range pages valid
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + *
> > > + * This function determines if a GPU SVM range pages are valid.
> > > Expected be
> > > + * called holding gpusvm->notifier_lock and as the last step before
> > > commiting a
> > > + * GPU binding.
> > > + *
> > > + * Returns:
> > > + * True if GPU SVM range has valid pages, False otherwise
> > > + */
> > > +bool drm_gpusvm_range_pages_valid(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range)
> > > +{
> > > + lockdep_assert_held(&gpusvm->notifier_lock);
> > > +
> > > + return range->flags.has_vram_pages || range-
> > > >flags.has_dma_mapping;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_pages_valid_unlocked - GPU SVM range pages valid
> > > unlocked
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + *
> > > + * This function determines if a GPU SVM range pages are valid.
> > > Expected be
> > > + * called without holding gpusvm->notifier_lock.
> > > + *
> > > + * Returns:
> > > + * True if GPU SVM range has valid pages, False otherwise
> > > + */
> > > +static bool
> > > +drm_gpusvm_range_pages_valid_unlocked(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range
> > > *range)
> > > +{
> > > + bool pages_valid;
> > > +
> > > + if (!range->pages)
> > > + return false;
> > > +
> > > + drm_gpusvm_notifier_lock(gpusvm);
> > > + pages_valid = drm_gpusvm_range_pages_valid(gpusvm, range);
> > > + if (!pages_valid && range->flags.kfree_mapping) {
> > > + kfree(range->dma_addr);
> > > + range->flags.kfree_mapping = false;
> > > + range->pages = NULL;
> > > + }
> > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > +
> > > + return pages_valid;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_get_pages - Get pages for a GPU SVM range
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + * @ctx: GPU SVM context
> > > + *
> > > + * This function gets pages for a GPU SVM range and ensures they are
> > > mapped for
> > > + * DMA access.
> > > + *
> > > + * Returns:
> > > + * 0 on success, negative error code on failure.
> > > + */
> > > +int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + const struct drm_gpusvm_ctx *ctx)
> > > +{
> >
> > Is it possible to split this function up to make it look more neat?
> >
> >
> > > + struct mmu_interval_notifier *notifier = &range->notifier-
> > > >notifier;
> > > + struct hmm_range hmm_range = {
> > > + .default_flags = HMM_PFN_REQ_FAULT | (ctx->read_only
> > > ? 0 :
> > > + HMM_PFN_REQ_WRITE),
> > > + .notifier = notifier,
> > > + .start = range->va.start,
> > > + .end = range->va.end,
> > > + .dev_private_owner = gpusvm-
> > > >device_private_page_owner,
> > > + };
> > > + struct mm_struct *mm = gpusvm->mm;
> > > + unsigned long timeout =
> > > + jiffies +
> > > msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > > + unsigned long i, j;
> > > + unsigned long npages = npages_in_range(range->va.start,
> > > range->va.end);
> > > + unsigned int order = 0;
> > > + unsigned long *pfns;
> > > + struct page **pages;
> > > + int err = 0;
> > > + bool vram_pages = !!range->flags.migrate_vram;
> > > + bool alloc_pfns = false, kfree_mapping;
> > > +
> > > +retry:
> > > + kfree_mapping = false;
> > > + hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
> > > + if (drm_gpusvm_range_pages_valid_unlocked(gpusvm, range))
> > > + return 0;
> > > +
> > > + if (range->notifier_seq == hmm_range.notifier_seq && range-
> > > >pages) {
> > > + if (ctx->prefault)
> > > + return 0;
> > > +
> > > + pfns = (unsigned long *)range->pages;
> > > + pages = range->pages;
> > > + goto map_pages;
> > > + }
> > > +
> > > + if (!range->pages) {
> > > + pfns = kvmalloc_array(npages, sizeof(*pfns),
> > > GFP_KERNEL);
> > > + if (!pfns)
> > > + return -ENOMEM;
> > > + alloc_pfns = true;
> > > + } else {
> > > + pfns = (unsigned long *)range->pages;
> > > + }
> > > +
> > > + if (!ctx->mmap_locked) {
> > > + if (!mmget_not_zero(mm)) {
> > > + err = -EFAULT;
> > > + goto err_out;
> > > + }
> > > + }
> > > +
> > > + hmm_range.hmm_pfns = pfns;
> > > + while (true) {
> > > + /* Must be checked after mmu_interval_read_begin */
> > > + if (range->flags.unmapped) {
> > > + err = -EFAULT;
> > > + break;
> > > + }
> > > +
> > > + if (!ctx->mmap_locked) {
> > > + /*
> > > + * XXX: HMM locking document indicates only
> > > a read-lock
> > > + * is required but there apears to be a
> > > window between
> > > + * the MMU_NOTIFY_MIGRATE event triggered in
> > > a CPU fault
> > > + * via migrate_vma_setup and the pages
> > > actually moving
> > > + * in migrate_vma_finalize in which this
> > > code can grab
> > > + * garbage pages. Grabbing the write-lock if
> > > the range
> > > + * is attached to vram appears to protect
> > > against this
> > > + * race.
> > > + */
> > > + if (vram_pages)
> > > + mmap_write_lock(mm);
> > > + else
> > > + mmap_read_lock(mm);
> > > + }
> > > + err = hmm_range_fault(&hmm_range);
> > > + if (!ctx->mmap_locked) {
> > > + if (vram_pages)
> > > + mmap_write_unlock(mm);
> > > + else
> > > + mmap_read_unlock(mm);
> > > + }
> > > +
> > > + if (err == -EBUSY) {
> > > + if (time_after(jiffies, timeout))
> > > + break;
> > > +
> > > + hmm_range.notifier_seq =
> > > mmu_interval_read_begin(notifier);
> > > + continue;
> > > + }
> > > + break;
> > > + }
> > > + if (!ctx->mmap_locked)
> > > + mmput(mm);
> > > + if (err)
> > > + goto err_free;
> > > +
> > > + pages = (struct page **)pfns;
> > > +
> > > + if (ctx->prefault) {
> > > + range->pages = pages;
> > > + goto set_seqno;
> > > + }
> > > +
> > > +map_pages:
> > > + if (is_device_private_page(hmm_pfn_to_page(pfns[0]))) {
> > > + WARN_ON_ONCE(!range->vram_allocation);
> > > +
> > > + for (i = 0; i < npages; ++i) {
> > > + pages[i] = hmm_pfn_to_page(pfns[i]);
> > > +
> > > + if
> > > (WARN_ON_ONCE(!is_device_private_page(pages[i]))) {
> > > + err = -EOPNOTSUPP;
> > > + goto err_free;
> > > + }
> > > + }
> > > +
> > > + /* Do not race with notifier unmapping pages */
> > > + drm_gpusvm_notifier_lock(gpusvm);
> > > + range->flags.has_vram_pages = true;
> > > + range->pages = pages;
> > > + if (mmu_interval_read_retry(notifier,
> > > hmm_range.notifier_seq)) {
> > > + err = -EAGAIN;
> > > + __drm_gpusvm_range_unmap_pages(gpusvm,
> > > range);
> > > + }
> > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > + } else {
> > > + dma_addr_t *dma_addr = (dma_addr_t *)pfns;
> > > +
> > > + for_each_dma_page(i, j, npages, order) {
> >
> > Here it looks like you're assuming that all pages are the same order?
> > With THP that's definitely not the case, (unless hmm somehow thinks
> > they are 4K pages). This probably work because we only end up here in
> > the HugeTLB case where all pages are forced to the same oder.
> >
>
> It assumes the order within a chunk (range size) is all the same. I
> thought THP pages order would always be 9 (2M). THP tests
> (*-large-malloc) seem to work on LNL.
>
> This falls apart if chunks are larger than 2M as the first 2M could be a
> THP and 2nd could not. We discussed that you were changing the dma addr
> to support mixed mappings and encode the order. That is likely correct
> and would fix this limitation of only supporting 1 order size for chunk.
>
> I may not get this in the rev but agree this should be fixed. We
> deferring fixing this be ok with you?
>
> fwiw I haven't seen any ROI on chunks being larger than 2M so Xe likely
> won't have chunks larger than that but agree the design should support
> this.
>
> Matt
>
> > > + if (WARN_ON_ONCE(i && order !=
> > > +
> > > hmm_pfn_to_map_order(pfns[i]))) {
> > > + err = -EOPNOTSUPP;
> > > + npages = i;
> > > + goto err_unmap;
> > > + }
> > > + order = hmm_pfn_to_map_order(pfns[i]);
> > > +
> > > + pages[j] = hmm_pfn_to_page(pfns[i]);
> > > + if
> > > (WARN_ON_ONCE(is_zone_device_page(pages[j]))) {
> > > + err = -EOPNOTSUPP;
> > > + npages = i;
> > > + goto err_unmap;
> > > + }
> > > +
> > > + set_page_dirty_lock(pages[j]);
> > > + mark_page_accessed(pages[j]);
> > > +
> > > + dma_addr[j] = dma_map_page(gpusvm->drm->dev,
> > > + pages[j], 0,
> > > + PAGE_SIZE <<
> > > order,
> > > +
> > > DMA_BIDIRECTIONAL);
> > > + if (dma_mapping_error(gpusvm->drm->dev,
> > > dma_addr[j])) {
> > > + err = -EFAULT;
> > > + npages = i;
> > > + goto err_unmap;
> > > + }
> > > + }
> > > +
> > > + /* Huge pages, reduce memory footprint */
> > > + if (order) {
> > > + dma_addr = kmalloc_array(j,
> > > sizeof(*dma_addr),
> > > + GFP_KERNEL);
> > > + if (dma_addr) {
> > > + for (i = 0; i < j; ++i)
> > > + dma_addr[i] =
> > > (dma_addr_t)pfns[i];
> > > + kvfree(pfns);
> > > + kfree_mapping = true;
> > > + } else {
> > > + dma_addr = (dma_addr_t *)pfns;
> > > + }
> > > + }
> > > +
> > > + /* Do not race with notifier unmapping pages */
> > > + drm_gpusvm_notifier_lock(gpusvm);
> > > + range->order = order;
> > > + range->flags.kfree_mapping = kfree_mapping;
> > > + range->flags.has_dma_mapping = true;
> > > + range->dma_addr = dma_addr;
> > > + range->vram_allocation = NULL;
> > > + if (mmu_interval_read_retry(notifier,
> > > hmm_range.notifier_seq)) {
> > > + err = -EAGAIN;
> > > + __drm_gpusvm_range_unmap_pages(gpusvm,
> > > range);
> > > + }
> > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > + }
> > > +
> > > + if (err == -EAGAIN)
> > > + goto retry;
> > > +set_seqno:
> > > + range->notifier_seq = hmm_range.notifier_seq;
> > > +
> > > + return 0;
> > > +
> > > +err_unmap:
> > > + for_each_dma_page(i, j, npages, order)
> > > + dma_unmap_page(gpusvm->drm->dev,
> > > + (dma_addr_t)pfns[j],
> > > + PAGE_SIZE << order,
> > > DMA_BIDIRECTIONAL);
> > > +err_free:
> > > + if (alloc_pfns)
> > > + kvfree(pfns);
> > > +err_out:
> > > + return err;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_range_unmap_pages - Unmap pages associated with a GPU
> > > SVM range
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + * @ctx: GPU SVM context
> > > + *
> > > + * This function unmaps pages associated with a GPU SVM range. If
> > > @in_notifier
> > > + * is set, it is assumed that gpusvm->notifier_lock is held in write
> > > mode; if it
> > > + * is clear, it acquires gpusvm->notifier_lock in read mode. Must be
> > > called on
> > > + * each GPU SVM range attached to notifier in gpusvm->ops-
> > > >invalidate for IOMMU
> > > + * security model.
> > > + */
> > > +void drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + const struct drm_gpusvm_ctx *ctx)
> > > +{
> > > + if (ctx->in_notifier)
> > > + lockdep_assert_held_write(&gpusvm->notifier_lock);
> > > + else
> > > + drm_gpusvm_notifier_lock(gpusvm);
> > > +
> > > + __drm_gpusvm_range_unmap_pages(gpusvm, range);
> > > +
> > > + if (!ctx->in_notifier)
> > > + drm_gpusvm_notifier_unlock(gpusvm);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migration_put_page - Put a migration page
> > > + * @page: Pointer to the page to put
> > > + *
> > > + * This function unlocks and puts a page.
> > > + */
> > > +static void drm_gpusvm_migration_put_page(struct page *page)
> > > +{
> > > + unlock_page(page);
> > > + put_page(page);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migration_put_pages - Put migration pages
> > > + * @npages: Number of pages
> > > + * @migrate_pfn: Array of migrate page frame numbers
> > > + *
> > > + * This function puts an array of pages.
> > > + */
> > > +static void drm_gpusvm_migration_put_pages(unsigned long npages,
> > > + unsigned long
> > > *migrate_pfn)
> > > +{
> > > + unsigned long i;
> > > +
> > > + for (i = 0; i < npages; ++i) {
> > > + if (!migrate_pfn[i])
> > > + continue;
> > > +
> > > + drm_gpusvm_migration_put_page(migrate_pfn_to_page(mi
> > > grate_pfn[i]));
> > > + migrate_pfn[i] = 0;
> > > + }
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_get_vram_page - Get a reference to a VRAM page
> > > + * @page: Pointer to the page
> > > + * @zdd: Pointer to the GPU SVM zone device data
> > > + *
> > > + * This function associates the given page with the specified GPU
> > > SVM zone
> > > + * device data and initializes it for zone device usage.
> > > + */
> > > +static void drm_gpusvm_get_vram_page(struct page *page,
> > > + struct drm_gpusvm_zdd *zdd)
> > > +{
> > > + page->zone_device_data = drm_gpusvm_zdd_get(zdd);
> > > + zone_device_page_init(page);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migrate_map_pages() - Map migration pages for GPU SVM
> > > migration
> > > + * @dev: The device for which the pages are being mapped
> > > + * @dma_addr: Array to store DMA addresses corresponding to mapped
> > > pages
> > > + * @migrate_pfn: Array of migrate page frame numbers to map
> > > + * @npages: Number of pages to map
> > > + * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL)
> > > + *
> > > + * This function maps pages of memory for migration usage in GPU
> > > SVM. It
> > > + * iterates over each page frame number provided in @migrate_pfn,
> > > maps the
> > > + * corresponding page, and stores the DMA address in the provided
> > > @dma_addr
> > > + * array.
> > > + *
> > > + * Return: 0 on success, -EFAULT if an error occurs during mapping.
> > > + */
> > > +static int drm_gpusvm_migrate_map_pages(struct device *dev,
> > > + dma_addr_t *dma_addr,
> > > + long unsigned int
> > > *migrate_pfn,
> > > + unsigned long npages,
> > > + enum dma_data_direction dir)
> > > +{
> > > + unsigned long i;
> > > +
> > > + for (i = 0; i < npages; ++i) {
> > > + struct page *page =
> > > migrate_pfn_to_page(migrate_pfn[i]);
> > > +
> > > + if (!page)
> > > + continue;
> > > +
> > > + if (WARN_ON_ONCE(is_zone_device_page(page)))
> > > + return -EFAULT;
> > > +
> > > + dma_addr[i] = dma_map_page(dev, page, 0, PAGE_SIZE,
> > > dir);
> > > + if (dma_mapping_error(dev, dma_addr[i]))
> > > + return -EFAULT;
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migrate_unmap_pages() - Unmap pages previously mapped
> > > for GPU SVM migration
> > > + * @dev: The device for which the pages were mapped
> > > + * @dma_addr: Array of DMA addresses corresponding to mapped pages
> > > + * @npages: Number of pages to unmap
> > > + * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL)
> > > + *
> > > + * This function unmaps previously mapped pages of memory for GPU
> > > Shared Virtual
> > > + * Memory (SVM). It iterates over each DMA address provided in
> > > @dma_addr, checks
> > > + * if it's valid and not already unmapped, and unmaps the
> > > corresponding page.
> > > + */
> > > +static void drm_gpusvm_migrate_unmap_pages(struct device *dev,
> > > + dma_addr_t *dma_addr,
> > > + unsigned long npages,
> > > + enum dma_data_direction
> > > dir)
> > > +{
> > > + unsigned long i;
> > > +
> > > + for (i = 0; i < npages; ++i) {
> > > + if (!dma_addr[i] || dma_mapping_error(dev,
> > > dma_addr[i]))
> > > + continue;
> > > +
> > > + dma_unmap_page(dev, dma_addr[i], PAGE_SIZE, dir);
> > > + }
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migrate_to_vram - Migrate GPU SVM range to VRAM
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + * failure of this function.
> > > + * @vram_allocation: Driver-private pointer to the VRAM allocation.
> > > The caller
> > > + * should hold a reference to the VRAM allocation,
> > > which
> > > + * should be dropped via ops->vram_allocation or
> > > upon the
> > > + * failure of this function.
> > > + * @ctx: GPU SVM context
> > > + *
> > > + * This function migrates the specified GPU SVM range to VRAM. It
> > > performs the
> > > + * necessary setup and invokes the driver-specific operations for
> > > migration to
> > > + * VRAM. Upon successful return, @vram_allocation can safely
> > > reference @range
> > > + * until ops->vram_release is called which only upon successful
> > > return.
> > > + *
> > > + * Returns:
> > > + * 0 on success, negative error code on failure.
> > > + */
> > > +int drm_gpusvm_migrate_to_vram(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + void *vram_allocation,
> > > + const struct drm_gpusvm_ctx *ctx)
> > > +{
> > > + u64 start = range->va.start, end = range->va.end;
> > > + struct migrate_vma migrate = {
> > > + .start = start,
> > > + .end = end,
> > > + .pgmap_owner = gpusvm->device_private_page_owner,
> > > + .flags = MIGRATE_VMA_SELECT_SYSTEM,
> > > + };
> > > + struct mm_struct *mm = gpusvm->mm;
> > > + unsigned long i, npages = npages_in_range(start, end);
> > > + struct vm_area_struct *vas;
> > > + struct drm_gpusvm_zdd *zdd = NULL;
> > > + struct page **pages;
> > > + dma_addr_t *dma_addr;
> > > + void *buf;
> > > + int err;
> > > +
> > > + if (!range->flags.migrate_vram)
> > > + return -EINVAL;
> > > +
> > > + if (!gpusvm->ops->populate_vram_pfn || !gpusvm->ops-
> > > >copy_to_vram ||
> > > + !gpusvm->ops->copy_to_sram)
> > > + return -EOPNOTSUPP;
> > > +
> > > + if (!ctx->mmap_locked) {
> > > + if (!mmget_not_zero(mm)) {
> > > + err = -EFAULT;
> > > + goto err_out;
> > > + }
> > > + mmap_write_lock(mm);
> > > + }
> > > +
> > > + mmap_assert_locked(mm);
> > > +
> > > + vas = vma_lookup(mm, start);
> > > + if (!vas) {
> > > + err = -ENOENT;
> > > + goto err_mmunlock;
> > > + }
> > > +
> > > + if (end > vas->vm_end || start < vas->vm_start) {
> > > + err = -EINVAL;
> > > + goto err_mmunlock;
> > > + }
> > > +
> > > + if (!vma_is_anonymous(vas)) {
> > > + err = -EBUSY;
> > > + goto err_mmunlock;
> > > + }
> > > +
> > > + buf = kvcalloc(npages, 2 * sizeof(*migrate.src) +
> > > sizeof(*dma_addr) +
> > > + sizeof(*pages), GFP_KERNEL);
> > > + if (!buf) {
> > > + err = -ENOMEM;
> > > + goto err_mmunlock;
> > > + }
> > > + dma_addr = buf + (2 * sizeof(*migrate.src) * npages);
> > > + pages = buf + (2 * sizeof(*migrate.src) + sizeof(*dma_addr))
> > > * npages;
> > > +
> > > + zdd = drm_gpusvm_zdd_alloc(range);
> > > + if (!zdd) {
> > > + err = -ENOMEM;
> > > + goto err_free;
> > > + }
> > > +
> > > + migrate.vma = vas;
> > > + migrate.src = buf;
> > > + migrate.dst = migrate.src + npages;
> > > +
> > > + err = migrate_vma_setup(&migrate);
> > > + if (err)
> > > + goto err_free;
> > > +
> > > + /*
> > > + * FIXME: Below cases, !migrate.cpages and migrate.cpages !=
> > > npages, not
> > > + * always an error. Need to revisit possible cases and how
> > > to handle. We
> > > + * could prefault on migrate.cpages != npages via
> > > hmm_range_fault.
> > > + */
> > > +
> > > + if (!migrate.cpages) {
> > > + err = -EFAULT;
> > > + goto err_free;
> > > + }
> > > +
> > > + if (migrate.cpages != npages) {
> > > + err = -EBUSY;
> > > + goto err_finalize;
> > > + }
> > > +
> > > + err = gpusvm->ops->populate_vram_pfn(gpusvm,
> > > vram_allocation, npages,
> > > + migrate.dst);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > + err = drm_gpusvm_migrate_map_pages(gpusvm->drm->dev,
> > > dma_addr,
> > > + migrate.src, npages,
> > > DMA_TO_DEVICE);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > + for (i = 0; i < npages; ++i) {
> > > + struct page *page = pfn_to_page(migrate.dst[i]);
> > > +
> > > + pages[i] = page;
> > > + migrate.dst[i] = migrate_pfn(migrate.dst[i]);
> > > + drm_gpusvm_get_vram_page(page, zdd);
> > > + }
> > > +
> > > + err = gpusvm->ops->copy_to_vram(gpusvm, pages, dma_addr,
> > > npages);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > + /* Upon success bind vram allocation to range and zdd */
> > > + range->vram_allocation = vram_allocation;
> > > + WRITE_ONCE(zdd->vram_allocation, vram_allocation); /*
> > > Owns ref */
> > > +
> > > +err_finalize:
> > > + if (err)
> > > + drm_gpusvm_migration_put_pages(npages, migrate.dst);
> > > + migrate_vma_pages(&migrate);
> > > + migrate_vma_finalize(&migrate);
> > > + drm_gpusvm_migrate_unmap_pages(gpusvm->drm->dev, dma_addr,
> > > npages,
> > > + DMA_TO_DEVICE);
> > > +err_free:
> > > + if (zdd)
> > > + drm_gpusvm_zdd_put(zdd);
> > > + kvfree(buf);
> > > +err_mmunlock:
> > > + if (!ctx->mmap_locked) {
> > > + mmap_write_unlock(mm);
> > > + mmput(mm);
> > > + }
> > > +err_out:
> > > + return err;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migrate_populate_sram_pfn - Populate SRAM PFNs for a
> > > VM area
> > > + * @vas: Pointer to the VM area structure, can be NULL
> > > + * @npages: Number of pages to populate
> > > + * @src_mpfn: Source array of migrate PFNs
> > > + * @mpfn: Array of migrate PFNs to populate
> > > + * @addr: Start address for PFN allocation
> > > + *
> > > + * This function populates the SRAM migrate page frame numbers
> > > (PFNs) for the
> > > + * specified VM area structure. It allocates and locks pages in the
> > > VM area for
> > > + * SRAM usage. If vas is non-NULL use alloc_page_vma for allocation,
> > > if NULL use
> > > + * alloc_page for allocation.
> > > + *
> > > + * Returns:
> > > + * 0 on success, negative error code on failure.
> > > + */
> > > +static int drm_gpusvm_migrate_populate_sram_pfn(struct
> > > vm_area_struct *vas,
> > > + unsigned long
> > > npages,
> > > + unsigned long
> > > *src_mpfn,
> > > + unsigned long *mpfn,
> > > u64 addr)
> > > +{
> > > + unsigned long i;
> > > +
> > > + for (i = 0; i < npages; ++i, addr += PAGE_SIZE) {
> > > + struct page *page;
> > > +
> > > + if (!(src_mpfn[i] & MIGRATE_PFN_MIGRATE))
> > > + continue;
> > > +
> > > + if (vas)
> > > + page = alloc_page_vma(GFP_HIGHUSER, vas,
> > > addr);
> > > + else
> > > + page = alloc_page(GFP_HIGHUSER);
> > > +
> > > + if (!page)
> > > + return -ENOMEM;
> > > +
> > > + lock_page(page);
> > > + mpfn[i] = migrate_pfn(page_to_pfn(page));
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_evict_to_sram - Evict GPU SVM range to SRAM
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + *
> > > + * Similar to __drm_gpusvm_migrate_to_sram but does not require mmap
> > > lock and
> > > + * migration done via migrate_device_* functions. Fallback path as
> > > it is
> > > + * preferred to issue migrations with mmap lock.
> > > + *
> > > + * Returns:
> > > + * 0 on success, negative error code on failure.
> > > + */
> > > +static int drm_gpusvm_evict_to_sram(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range)
> > > +{
> > > + unsigned long npages;
> > > + struct page **pages;
> > > + unsigned long *src, *dst;
> > > + dma_addr_t *dma_addr;
> > > + void *buf;
> > > + int i, err = 0;
> > > +
> > > + npages = npages_in_range(range->va.start, range->va.end);
> > > +
> > > + buf = kvcalloc(npages, 2 * sizeof(*src) + sizeof(*dma_addr)
> > > +
> > > + sizeof(*pages), GFP_KERNEL);
> > > + if (!buf) {
> > > + err = -ENOMEM;
> > > + goto err_out;
> > > + }
> > > + src = buf;
> > > + dst = buf + (sizeof(*src) * npages);
> > > + dma_addr = buf + (2 * sizeof(*src) * npages);
> > > + pages = buf + (2 * sizeof(*src) + sizeof(*dma_addr)) *
> > > npages;
> > > +
> > > + err = gpusvm->ops->populate_vram_pfn(gpusvm, range-
> > > >vram_allocation,
> > > + npages, src);
> > > + if (err)
> > > + goto err_free;
> > > +
> > > + err = migrate_device_vma_range(gpusvm->mm,
> > > + gpusvm-
> > > >device_private_page_owner, src,
> > > + npages, range->va.start);
> > > + if (err)
> > > + goto err_free;
> > > +
> > > + err = drm_gpusvm_migrate_populate_sram_pfn(NULL, npages,
> > > src, dst, 0);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > + err = drm_gpusvm_migrate_map_pages(gpusvm->drm->dev,
> > > dma_addr,
> > > + dst, npages,
> > > DMA_BIDIRECTIONAL);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > + for (i = 0; i < npages; ++i)
> > > + pages[i] = migrate_pfn_to_page(src[i]);
> > > +
> > > + err = gpusvm->ops->copy_to_sram(gpusvm, pages, dma_addr,
> > > npages);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > +err_finalize:
> > > + if (err)
> > > + drm_gpusvm_migration_put_pages(npages, dst);
> > > + migrate_device_pages(src, dst, npages);
> > > + migrate_device_finalize(src, dst, npages);
> > > + drm_gpusvm_migrate_unmap_pages(gpusvm->drm->dev, dma_addr,
> > > npages,
> > > + DMA_BIDIRECTIONAL);
> > > +err_free:
> > > + kvfree(buf);
> > > +err_out:
> > > +
> > > + return err;
> > > +}
> > > +
> > > +/**
> > > + * __drm_gpusvm_migrate_to_sram - Migrate GPU SVM range to SRAM
> > > (internal)
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @vas: Pointer to the VM area structure
> > > + * @page: Pointer to the page for fault handling (can be NULL)
> > > + * @start: Start address of the migration range
> > > + * @end: End address of the migration range
> > > + *
> > > + * This internal function performs the migration of the specified
> > > GPU SVM range
> > > + * to SRAM. It sets up the migration, populates + dma maps SRAM
> > > PFNs, and
> > > + * invokes the driver-specific operations for migration to SRAM.
> > > + *
> > > + * Returns:
> > > + * 0 on success, negative error code on failure.
> > > + */
> > > +static int __drm_gpusvm_migrate_to_sram(struct drm_gpusvm *gpusvm,
> > > + struct vm_area_struct *vas,
> > > + struct page *page,
> > > + u64 start, u64 end)
> > > +{
> > > + struct migrate_vma migrate = {
> > > + .vma = vas,
> > > + .pgmap_owner = gpusvm->device_private_page_owner,
> > > + .flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE,
> > > + .fault_page = page,
> > > + };
> > > + unsigned long npages;
> > > + struct page **pages;
> > > + dma_addr_t *dma_addr;
> > > + void *buf;
> > > + int i, err = 0;
> > > +
> > > + mmap_assert_locked(gpusvm->mm);
> > > +
> > > + /* Corner where VMA area struct has been partially unmapped
> > > */
> > > + if (start < vas->vm_start)
> > > + start = vas->vm_start;
> > > + if (end > vas->vm_end)
> > > + end = vas->vm_end;
> > > +
> > > + migrate.start = start;
> > > + migrate.end = end;
> > > + npages = npages_in_range(start, end);
> > > +
> > > + buf = kvcalloc(npages, 2 * sizeof(*migrate.src) +
> > > sizeof(*dma_addr) +
> > > + sizeof(*pages), GFP_KERNEL);
> > > + if (!buf) {
> > > + err = -ENOMEM;
> > > + goto err_out;
> > > + }
> > > + dma_addr = buf + (2 * sizeof(*migrate.src) * npages);
> > > + pages = buf + (2 * sizeof(*migrate.src) + sizeof(*dma_addr))
> > > * npages;
> > > +
> > > + migrate.vma = vas;
> > > + migrate.src = buf;
> > > + migrate.dst = migrate.src + npages;
> > > +
> > > + err = migrate_vma_setup(&migrate);
> > > + if (err)
> > > + goto err_free;
> > > +
> > > + /* Raced with another CPU fault, nothing to do */
> > > + if (!migrate.cpages)
> > > + goto err_free;
> > > +
> > > + err = drm_gpusvm_migrate_populate_sram_pfn(vas, npages,
> > > + migrate.src,
> > > migrate.dst,
> > > + start);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > + err = drm_gpusvm_migrate_map_pages(gpusvm->drm->dev,
> > > dma_addr,
> > > + migrate.dst, npages,
> > > + DMA_BIDIRECTIONAL);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > + for (i = 0; i < npages; ++i)
> > > + pages[i] = migrate_pfn_to_page(migrate.src[i]);
> > > +
> > > + err = gpusvm->ops->copy_to_sram(gpusvm, pages, dma_addr,
> > > npages);
> > > + if (err)
> > > + goto err_finalize;
> > > +
> > > +err_finalize:
> > > + if (err)
> > > + drm_gpusvm_migration_put_pages(npages, migrate.dst);
> > > + migrate_vma_pages(&migrate);
> > > + migrate_vma_finalize(&migrate);
> > > + drm_gpusvm_migrate_unmap_pages(gpusvm->drm->dev, dma_addr,
> > > npages,
> > > + DMA_BIDIRECTIONAL);
> > > +err_free:
> > > + kvfree(buf);
> > > +err_out:
> > > + mmap_assert_locked(gpusvm->mm);
> > > +
> > > + return err;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migrate_to_sram - Migrate (evict) GPU SVM range to
> > > SRAM
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @range: Pointer to the GPU SVM range structure
> > > + * @ctx: GPU SVM context
> > > + *
> > > + * This function initiates the migration of the specified GPU SVM
> > > range to
> > > + * SRAM. It performs necessary checks and invokes the internal
> > > migration
> > > + * function for actual migration.
> > > + *
> > > + * Returns:
> > > + * 0 on success, negative error code on failure.
> > > + */
> > > +int drm_gpusvm_migrate_to_sram(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + const struct drm_gpusvm_ctx *ctx)
> > > +{
> > > + u64 start = range->va.start, end = range->va.end;
> > > + struct mm_struct *mm = gpusvm->mm;
> > > + struct vm_area_struct *vas;
> > > + int err;
> > > + bool retry = false;
> > > +
> > > + if (!ctx->mmap_locked) {
> > > + if (!mmget_not_zero(mm)) {
> > > + err = -EFAULT;
> > > + goto err_out;
> > > + }
> > > + if (ctx->trylock_mmap) {
> > > + if (!mmap_read_trylock(mm)) {
> > > + err =
> > > drm_gpusvm_evict_to_sram(gpusvm, range);
> > > + goto err_mmput;
> > > + }
> > > + } else {
> > > + mmap_read_lock(mm);
> > > + }
> > > + }
> > > +
> > > + mmap_assert_locked(mm);
> > > +
> > > + /*
> > > + * Loop required to find all VMA area structs for the corner
> > > case when
> > > + * VRAM backing has been partially unmapped from MM's
> > > address space.
> > > + */
> > > +again:
> > > + vas = find_vma(mm, start);
> > > + if (!vas) {
> > > + if (!retry)
> > > + err = -ENOENT;
> > > + goto err_mmunlock;
> > > + }
> > > +
> > > + if (end <= vas->vm_start || start >= vas->vm_end) {
> > > + if (!retry)
> > > + err = -EINVAL;
> > > + goto err_mmunlock;
> > > + }
> > > +
> > > + err = __drm_gpusvm_migrate_to_sram(gpusvm, vas, NULL, start,
> > > end);
> > > + if (err)
> > > + goto err_mmunlock;
> > > +
> > > + if (vas->vm_end < end) {
> > > + retry = true;
> > > + start = vas->vm_end;
> > > + goto again;
> > > + }
> > > +
> > > + if (!ctx->mmap_locked) {
> > > + mmap_read_unlock(mm);
> > > + /*
> > > + * Using mmput_async as this function can be called
> > > while
> > > + * holding a dma-resv lock, and a final put can grab
> > > the mmap
> > > + * lock, causing a lock inversion.
> > > + */
> > > + mmput_async(mm);
> > > + }
> > > +
> > > + return 0;
> > > +
> > > +err_mmunlock:
> > > + if (!ctx->mmap_locked)
> > > + mmap_read_unlock(mm);
> > > +err_mmput:
> > > + if (!ctx->mmap_locked)
> > > + mmput_async(mm);
> > > +err_out:
> > > + return err;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_page_free - Put GPU SVM zone device data associated
> > > with a page
> > > + * @page: Pointer to the page
> > > + *
> > > + * This function is a callback used to put the GPU SVM zone device
> > > data
> > > + * associated with a page when it is being released.
> > > + */
> > > +static void drm_gpusvm_page_free(struct page *page)
> > > +{
> > > + drm_gpusvm_zdd_put(page->zone_device_data);
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_migrate_to_ram - Migrate GPU SVM range to RAM (page
> > > fault handler)
> > > + * @vmf: Pointer to the fault information structure
> > > + *
> > > + * This function is a page fault handler used to migrate a GPU SVM
> > > range to RAM.
> > > + * It retrieves the GPU SVM range information from the faulting page
> > > and invokes
> > > + * the internal migration function to migrate the range back to RAM.
> > > + *
> > > + * Returns:
> > > + * VM_FAULT_SIGBUS on failure, 0 on success.
> > > + */
> > > +static vm_fault_t drm_gpusvm_migrate_to_ram(struct vm_fault *vmf)
> > > +{
> > > + struct drm_gpusvm_zdd *zdd = vmf->page->zone_device_data;
> > > + int err;
> > > +
> > > + err = __drm_gpusvm_migrate_to_sram(zdd->range->gpusvm,
> > > + vmf->vma, vmf->page,
> > > + zdd->range->va.start,
> > > + zdd->range->va.end);
> > > +
> > > + return err ? VM_FAULT_SIGBUS : 0;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_pagemap_ops - Device page map operations for GPU SVM
> > > + */
> > > +static const struct dev_pagemap_ops drm_gpusvm_pagemap_ops = {
> > > + .page_free = drm_gpusvm_page_free,
> > > + .migrate_to_ram = drm_gpusvm_migrate_to_ram,
> > > +};
> > > +
> > > +/**
> > > + * drm_gpusvm_pagemap_ops_get - Retrieve GPU SVM device page map
> > > operations
> > > + *
> > > + * Returns:
> > > + * Pointer to the GPU SVM device page map operations structure.
> > > + */
> > > +const struct dev_pagemap_ops *drm_gpusvm_pagemap_ops_get(void)
> > > +{
> > > + return &drm_gpusvm_pagemap_ops;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_has_mapping - Check if GPU SVM has mapping for the
> > > given address range
> > > + * @gpusvm: Pointer to the GPU SVM structure.
> > > + * @start: Start address
> > > + * @end: End address
> > > + *
> > > + * Returns:
> > > + * True if GPU SVM has mapping, False otherwise
> > > + */
> > > +bool drm_gpusvm_has_mapping(struct drm_gpusvm *gpusvm, u64 start,
> > > u64 end)
> > > +{
> > > + struct drm_gpusvm_notifier *notifier;
> > > +
> > > + drm_gpusvm_for_each_notifier(notifier, gpusvm, start, end) {
> > > + struct drm_gpusvm_range *range = NULL;
> > > +
> > > + drm_gpusvm_for_each_range(range, notifier, start,
> > > end)
> > > + return true;
> > > + }
> > > +
> > > + return false;
> > > +}
> > > diff --git a/drivers/gpu/drm/xe/drm_gpusvm.h
> > > b/drivers/gpu/drm/xe/drm_gpusvm.h
> > > new file mode 100644
> > > index 000000000000..0ea70f8534a8
> > > --- /dev/null
> > > +++ b/drivers/gpu/drm/xe/drm_gpusvm.h
> > > @@ -0,0 +1,415 @@
> > > +/* SPDX-License-Identifier: MIT */
> > > +/*
> > > + * Copyright © 2024 Intel Corporation
> > > + */
> > > +
> > > +#ifndef __DRM_GPUSVM_H__
> > > +#define __DRM_GPUSVM_H__
> > > +
> > > +#include <linux/kref.h>
> > > +#include <linux/mmu_notifier.h>
> > > +#include <linux/workqueue.h>
> > > +
> > > +struct dev_pagemap_ops;
> > > +struct drm_device;
> > > +struct drm_gpusvm;
> > > +struct drm_gpusvm_notifier;
> > > +struct drm_gpusvm_ops;
> > > +struct drm_gpusvm_range;
> > > +
> > > +/**
> > > + * struct drm_gpusvm_ops - Operations structure for GPU SVM
> > > + *
> > > + * This structure defines the operations for GPU Shared Virtual
> > > Memory (SVM).
> > > + * These operations are provided by the GPU driver to manage SVM
> > > ranges and
> > > + * perform operations such as migration between VRAM and system RAM.
> > > + */
> > > +struct drm_gpusvm_ops {
> > > + /**
> > > + * @notifier_alloc: Allocate a GPU SVM notifier (optional)
> > > + *
> > > + * This function shall allocate a GPU SVM notifier.
> > > + *
> > > + * Returns:
> > > + * Pointer to the allocated GPU SVM notifier on success,
> > > NULL on failure.
> > > + */
> > > + struct drm_gpusvm_notifier *(*notifier_alloc)(void);
> > > +
> > > + /**
> > > + * @notifier_free: Free a GPU SVM notifier (optional)
> > > + * @notifier: Pointer to the GPU SVM notifier to be freed
> > > + *
> > > + * This function shall free a GPU SVM notifier.
> > > + */
> > > + void (*notifier_free)(struct drm_gpusvm_notifier *notifier);
> > > +
> > > + /**
> > > + * @range_alloc: Allocate a GPU SVM range (optional)
> > > + * @gpusvm: Pointer to the GPU SVM
> > > + *
> > > + * This function shall allocate a GPU SVM range.
> > > + *
> > > + * Returns:
> > > + * Pointer to the allocated GPU SVM range on success, NULL
> > > on failure.
> > > + */
> > > + struct drm_gpusvm_range *(*range_alloc)(struct drm_gpusvm
> > > *gpusvm);
> > > +
> > > + /**
> > > + * @range_free: Free a GPU SVM range (optional)
> > > + * @range: Pointer to the GPU SVM range to be freed
> > > + *
> > > + * This function shall free a GPU SVM range.
> > > + */
> > > + void (*range_free)(struct drm_gpusvm_range *range);
> > > +
> > > + /**
> > > + * @vram_release: Release VRAM allocation (optional)
> > > + * @vram_allocation: Driver-private pointer to the VRAM
> > > allocation
> > > + *
> > > + * This function shall release VRAM allocation and expects
> > > to drop a
> > > + * reference to VRAM allocation.
> > > + */
> > > + void (*vram_release)(void *vram_allocation);
> > > +
> > > + /**
> > > + * @populate_vram_pfn: Populate VRAM PFN (required for
> > > migration)
> > > + * @gpusvm: Pointer to the GPU SVM
> > > + * @vram_allocation: Driver-private pointer to the VRAM
> > > allocation
> > > + * @npages: Number of pages to populate
> > > + * @pfn: Array of page frame numbers to populate
> > > + *
> > > + * This function shall populate VRAM page frame numbers
> > > (PFN).
> > > + *
> > > + * Returns:
> > > + * 0 on success, a negative error code on failure.
> > > + */
> > > + int (*populate_vram_pfn)(struct drm_gpusvm *gpusvm,
> > > + void *vram_allocation,
> > > + unsigned long npages,
> > > + unsigned long *pfn);
> > > +
> > > + /**
> > > + * @copy_to_vram: Copy to VRAM (required for migration)
> > > + * @gpusvm: Pointer to the GPU SVM
> > > + * @pages: Pointer to array of VRAM pages (destination)
> > > + * @dma_addr: Pointer to array of DMA addresses (source)
> > > + * @npages: Number of pages to copy
> > > + *
> > > + * This function shall copy pages to VRAM.
> > > + *
> > > + * Returns:
> > > + * 0 on success, a negative error code on failure.
> > > + */
> > > + int (*copy_to_vram)(struct drm_gpusvm *gpusvm,
> > > + struct page **pages,
> > > + dma_addr_t *dma_addr,
> > > + unsigned long npages);
> > > +
> > > + /**
> > > + * @copy_to_sram: Copy to system RAM (required for
> > > migration)
> > > + * @gpusvm: Pointer to the GPU SVM
> > > + * @pages: Pointer to array of VRAM pages (source)
> > > + * @dma_addr: Pointer to array of DMA addresses
> > > (destination)
> > > + * @npages: Number of pages to copy
> > > + *
> > > + * This function shall copy pages to system RAM.
> > > + *
> > > + * Returns:
> > > + * 0 on success, a negative error code on failure.
> > > + */
> > > + int (*copy_to_sram)(struct drm_gpusvm *gpusvm,
> > > + struct page **pages,
> > > + dma_addr_t *dma_addr,
> > > + unsigned long npages);
> > > +
> > > + /**
> > > + * @invalidate: Invalidate GPU SVM notifier (required)
> > > + * @gpusvm: Pointer to the GPU SVM
> > > + * @notifier: Pointer to the GPU SVM notifier
> > > + * @mmu_range: Pointer to the mmu_notifier_range structure
> > > + *
> > > + * This function shall invalidate the GPU page tables. It
> > > can safely
> > > + * walk the notifier range RB tree/list in this function.
> > > Called while
> > > + * holding the notifier lock.
> > > + */
> > > + void (*invalidate)(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_notifier *notifier,
> > > + const struct mmu_notifier_range
> > > *mmu_range);
> > > +};
> > > +
> > > +/**
> > > + * struct drm_gpusvm_notifier - Structure representing a GPU SVM
> > > notifier
> > > + *
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @notifier: MMU interval notifier
> > > + * @interval: Interval for the notifier
> > > + * @rb: Red-black tree node for the parent GPU SVM structure
> > > notifier tree
> > > + * @root: Cached root node of the RB tree containing ranges
> > > + * @range_list: List head containing of ranges in the same order
> > > they appear in
> > > + * interval tree. This is useful to keep iterating
> > > ranges while
> > > + * doing modifications to RB tree.
> > > + * @flags.removed: Flag indicating whether the MMU interval notifier
> > > has been
> > > + * removed
> > > + *
> > > + * This structure represents a GPU SVM notifier.
> > > + */
> > > +struct drm_gpusvm_notifier {
> > > + struct drm_gpusvm *gpusvm;
> > > + struct mmu_interval_notifier notifier;
> > > + struct {
> > > + u64 start;
> > > + u64 end;
> > > + } interval;
> > > + struct {
> > > + struct rb_node node;
> > > + struct list_head entry;
> > > + u64 __subtree_last;
> > > + } rb;
> > > + struct rb_root_cached root;
> > > + struct list_head range_list;
> > > + struct {
> > > + u32 removed : 1;
> > > + } flags;
> > > +};
> > > +
> > > +/**
> > > + * struct drm_gpusvm_range - Structure representing a GPU SVM range
> > > + *
> > > + * @gpusvm: Pointer to the GPU SVM structure
> > > + * @notifier: Pointer to the GPU SVM notifier
> > > + * @refcount: Reference count for the range
> > > + * @rb: Red-black tree node for the parent GPU SVM notifier
> > > structure range tree
> > > + * @va: Virtual address range
> > > + * @notifier_seq: Notifier sequence number of the range's pages
> > > + * @pages: Pointer to the array of pages (if backing store is in
> > > VRAM)
> > > + * @dma_addr: DMA address array (if backing store is SRAM and DMA
> > > mapped)
> > > + * @vram_allocation: Driver-private pointer to the VRAM allocation
> > > + * @order: Order of dma mapping. i.e. PAGE_SIZE << order is mapping
> > > size
> > > + * @flags.migrate_vram: Flag indicating whether the range can be
> > > migrated to VRAM
> > > + * @flags.unmapped: Flag indicating if the range has been unmapped
> > > + * @flags.partial_unmap: Flag indicating if the range has been
> > > partially unmapped
> > > + * @flags.has_vram_pages: Flag indicating if the range has vram
> > > pages
> > > + * @flags.has_dma_mapping: Flag indicating if the range has a DMA
> > > mapping
> > > + * @flags.kfree_mapping: Flag indicating @dma_addr is a compact
> > > allocation based
> > > + * on @order which releases via kfree
> > > + *
> > > + * This structure represents a GPU SVM range used for tracking
> > > memory ranges
> > > + * mapped in a DRM device.
> > > + */
> > > +struct drm_gpusvm_range {
> > > + struct drm_gpusvm *gpusvm;
> > > + struct drm_gpusvm_notifier *notifier;
> > > + struct kref refcount;
> > > + struct {
> > > + struct rb_node node;
> > > + struct list_head entry;
> > > + u64 __subtree_last;
> > > + } rb;
> > > + struct {
> > > + u64 start;
> > > + u64 end;
> > > + } va;
> > > + unsigned long notifier_seq;
> > > + union {
> > > + struct page **pages;
> > > + dma_addr_t *dma_addr;
> > > + };
> > > + void *vram_allocation;
> > > + u16 order;
> > > + struct {
> > > + /* All flags below must be set upon creation */
> > > + u16 migrate_vram : 1;
> > > + /* All flags below must be set / cleared under
> > > notifier lock */
> > > + u16 unmapped : 1;
> > > + u16 partial_unmap : 1;
> > > + u16 has_vram_pages : 1;
> > > + u16 has_dma_mapping : 1;
> > > + u16 kfree_mapping : 1;
> > > + } flags;
> > > +};
> > > +
> > > +/**
> > > + * struct drm_gpusvm - GPU SVM structure
> > > + *
> > > + * @name: Name of the GPU SVM
> > > + * @drm: Pointer to the DRM device structure
> > > + * @mm: Pointer to the mm_struct for the address space
> > > + * @device_private_page_owner: Device private pages owner
> > > + * @mm_start: Start address of GPU SVM
> > > + * @mm_range: Range of the GPU SVM
> > > + * @notifier_size: Size of individual notifiers
> > > + * @ops: Pointer to the operations structure for GPU SVM
> > > + * @chunk_sizes: Pointer to the array of chunk sizes used in range
> > > allocation.
> > > + * Entries should be powers of 2 in descending order.
> > > + * @num_chunks: Number of chunks
> > > + * @notifier_lock: Read-write semaphore for protecting notifier
> > > operations
> > > + * @zdd_wq: Workqueue for deferred work on zdd destruction
> > > + * @root: Cached root node of the Red-Black tree containing GPU SVM
> > > notifiers
> > > + * @notifier_list: list head containing of notifiers in the same
> > > order they
> > > + * appear in interval tree. This is useful to keep
> > > iterating
> > > + * notifiers while doing modifications to RB tree.
> > > + *
> > > + * This structure represents a GPU SVM (Shared Virtual Memory) used
> > > for tracking
> > > + * memory ranges mapped in a DRM (Direct Rendering Manager) device.
> > > + *
> > > + * No reference counting is provided, as this is expected to be
> > > embedded in the
> > > + * driver VM structure along with the struct drm_gpuvm, which
> > > handles reference
> > > + * counting.
> > > + */
> > > +struct drm_gpusvm {
> > > + const char *name;
> > > + struct drm_device *drm;
> > > + struct mm_struct *mm;
> > > + void *device_private_page_owner;
> > > + u64 mm_start;
> > > + u64 mm_range;
> > > + u64 notifier_size;
> > > + const struct drm_gpusvm_ops *ops;
> > > + const u64 *chunk_sizes;
> > > + int num_chunks;
> > > + struct rw_semaphore notifier_lock;
> > > + struct workqueue_struct *zdd_wq;
> > > + struct rb_root_cached root;
> > > + struct list_head notifier_list;
> > > +};
> > > +
> > > +/**
> > > + * struct drm_gpusvm_ctx - DRM GPU SVM context
> > > + *
> > > + * @mmap_locked: mmap lock is locked
> > > + * @trylock_mmap: trylock mmap lock, used to avoid locking
> > > inversions
> > > + * (e.g.dma-revs -> mmap lock)
> > > + * @in_notifier: entering from a MMU notifier
> > > + * @read_only: operating on read-only memory
> > > + * @vram_possible: possible to use VRAM
> > > + * @prefault: prefault pages
> > > + *
> > > + * Context that is DRM GPUSVM is operating in (i.e. user arguments).
> > > + */
> > > +struct drm_gpusvm_ctx {
> > > + u32 mmap_locked :1;
> > > + u32 trylock_mmap :1;
> > > + u32 in_notifier :1;
> > > + u32 read_only :1;
> > > + u32 vram_possible :1;
> > > + u32 prefault :1;
> > > +};
> > > +
> > > +int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
> > > + const char *name, struct drm_device *drm,
> > > + struct mm_struct *mm, void
> > > *device_private_page_owner,
> > > + u64 mm_start, u64 mm_range, u64 notifier_size,
> > > + const struct drm_gpusvm_ops *ops,
> > > + const u64 *chunk_sizes, int num_chunks);
> > > +void drm_gpusvm_fini(struct drm_gpusvm *gpusvm);
> > > +void drm_gpusvm_free(struct drm_gpusvm *gpusvm);
> > > +
> > > +struct drm_gpusvm_range *
> > > +drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm, u64
> > > fault_addr,
> > > + u64 gpuva_start, u64 gpuva_end,
> > > + const struct drm_gpusvm_ctx *ctx);
> > > +void drm_gpusvm_range_remove(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range);
> > > +
> > > +struct drm_gpusvm_range *
> > > +drm_gpusvm_range_get(struct drm_gpusvm_range *range);
> > > +void drm_gpusvm_range_put(struct drm_gpusvm_range *range);
> > > +
> > > +bool drm_gpusvm_range_pages_valid(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range);
> > > +
> > > +int drm_gpusvm_range_get_pages(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + const struct drm_gpusvm_ctx *ctx);
> > > +void drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + const struct drm_gpusvm_ctx *ctx);
> > > +
> > > +int drm_gpusvm_migrate_to_vram(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + void *vram_allocation,
> > > + const struct drm_gpusvm_ctx *ctx);
> > > +int drm_gpusvm_migrate_to_sram(struct drm_gpusvm *gpusvm,
> > > + struct drm_gpusvm_range *range,
> > > + const struct drm_gpusvm_ctx *ctx);
> > > +
> > > +const struct dev_pagemap_ops *drm_gpusvm_pagemap_ops_get(void);
> > > +
> > > +bool drm_gpusvm_has_mapping(struct drm_gpusvm *gpusvm, u64 start,
> > > u64 end);
> > > +
> > > +struct drm_gpusvm_range *
> > > +drm_gpusvm_range_find(struct drm_gpusvm_notifier *notifier, u64
> > > start, u64 end);
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_lock - Lock GPU SVM notifier
> > > + * @gpusvm__: Pointer to the GPU SVM structure.
> > > + *
> > > + * Abstract client usage GPU SVM notifier lock, take lock
> > > + */
> > > +#define drm_gpusvm_notifier_lock(gpusvm__) \
> > > + down_read(&(gpusvm__)->notifier_lock)
> > > +
> > > +/**
> > > + * drm_gpusvm_notifier_unlock - Unlock GPU SVM notifier
> > > + * @gpusvm__: Pointer to the GPU SVM structure.
> > > + *
> > > + * Abstract client usage GPU SVM notifier lock, drop lock
> > > + */
> > > +#define drm_gpusvm_notifier_unlock(gpusvm__) \
> > > + up_read(&(gpusvm__)->notifier_lock)
> > > +
> > > +/**
> > > + * __drm_gpusvm_range_next - Get the next GPU SVM range in the list
> > > + * @range: a pointer to the current GPU SVM range
> > > + *
> > > + * Return: A pointer to the next drm_gpusvm_range if available, or
> > > NULL if the
> > > + * current range is the last one or if the input range is
> > > NULL.
> > > + */
> > > +static inline struct drm_gpusvm_range *
> > > +__drm_gpusvm_range_next(struct drm_gpusvm_range *range)
> > > +{
> > > + if (range && !list_is_last(&range->rb.entry,
> > > + &range->notifier->range_list))
> > > + return list_next_entry(range, rb.entry);
> > > +
> > > + return NULL;
> > > +}
> > > +
> > > +/**
> > > + * drm_gpusvm_for_each_range - Iterate over GPU SVM ranges in a
> > > notifier
> > > + * @range__: Iterator variable for the ranges. If set, it indicates
> > > the start of
> > > + * the iterator. If NULL, call drm_gpusvm_range_find() to
> > > get the range.
> > > + * @notifier__: Pointer to the GPU SVM notifier
> > > + * @start__: Start address of the range
> > > + * @end__: End address of the range
> > > + *
> > > + * This macro is used to iterate over GPU SVM ranges in a notifier.
> > > It is safe
> > > + * to use while holding the driver SVM lock or the notifier lock.
> > > + */
> > > +#define drm_gpusvm_for_each_range(range__, notifier__, start__,
> > > end__) \
> > > + for ((range__) = (range__)
> > > ?: \
> > > + drm_gpusvm_range_find((notifier__), (start__),
> > > (end__)); \
> > > + (range__) && (range__->va.start <
> > > (end__)); \
> > > + (range__) = __drm_gpusvm_range_next(range__))
> > > +
> > > +/**
> > > + * drm_gpusvm_range_set_unmapped - Mark a GPU SVM range as unmapped
> > > + * @range: Pointer to the GPU SVM range structure.
> > > + * @mmu_range: Pointer to the MMU notifier range structure.
> > > + *
> > > + * This function marks a GPU SVM range as unmapped and sets the
> > > partial_unmap flag
> > > + * if the range partially falls within the provided MMU notifier
> > > range.
> > > + */
> > > +static inline void
> > > +drm_gpusvm_range_set_unmapped(struct drm_gpusvm_range *range,
> > > + const struct mmu_notifier_range
> > > *mmu_range)
> > > +{
> > > + lockdep_assert_held_write(&range->gpusvm->notifier_lock);
> > > +
> > > + range->flags.unmapped = true;
> > > + if (range->va.start < mmu_range->start ||
> > > + range->va.end > mmu_range->end)
> > > + range->flags.partial_unmap = true;
> > > +}
> > > +
> > > +#endif /* __DRM_GPUSVM_H__ */
> >
