On Wed, Oct 16, 2024 at 08:27:51AM +0200, Thomas Hellström wrote:
> On Wed, 2024-10-16 at 03:18 +0000, Matthew Brost wrote:
> > On Wed, Oct 09, 2024 at 12:50:42PM +0200, Thomas Hellström wrote:
> > > Hi, Matthew.
> > >
> > > Some comments below around migrating to SRAM.
> > >
> > >
> > > 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.
> > > >
> > > > 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);
> > > > +
> > > > +/**
> > > > + * 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;
> > > > + void *vram_allocation;
> > > > +};
> > > > +
> > > > +/**
> > > > + * 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)
> > > > +{
> > > > + 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) {
> > > > + 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_pag
> > > > e(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]);
> > >
> > > See comments below which pages we actually want to migrate.
> > >
> > >
> > > > +
> > > > + 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);
> > >
> > > This function is typically called from the vm side to get a clean
> > > mm as
> > > a last resort after get_pages() fail. As such should we have it
> > > evict
> > > *everything*, even foreign device memory, and mismatching local
> > > device
> > > pages. If so, we could use hmm_range_fault() with a NULL page owner
> > > +
> > > faulting to do that.
> > >
> >
> > I've actually tried that and it seemed to mostly work well and
> > actually
> > would be my preference as this avoids a VMA lookup in GPU SVM.
> >
> > I think it is problem though if some of the pages are partially
> > unmapped
> > though as hmm_range_fault will abort if fault cannot be resolved.
> > Maybe
> > I'm mistaken on this. I won't get this in rev2 but will put this on
> > my
> > list to continue to play around with.
>
> OK. Presumably if faulting fails we should try a narrower range unless
> the page actually hitting the gpu pagefault is unmapped, to ensure we
> make progress rather than aborting?
>
I think the easiest thing would be add a flag to HMM that says continue
on fault failure. Now I remember another issue, hmm_range_fault doesn't
work for coherent pages if we ever decide to use them.
Maybe we can do something like hmm_range_fault without fault bit set to
collect device pages and then use migrate_device_* functions to evict.
Think drm_gpusvm_evict_to_ram in v2 (just posted) with
populate_devmem_pfn replaced with hmm_range_fault. That seems like this
would work. Maybe I'm missing a race here though, likely gets racier
with multi-GPU too but seems workable.
>
> >
> > > > + 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);
> > >
> > > When called from here, since this is a pagemap op, we should ensure
> > > we
> > > only migrate our own pagemap to RAM?
> > >
> >
> > I think you resolve this with the following the patch [1], right? I
> > think I agree.
>
> It doesn't fully resolve it, but adds the capability to do more
> specified filtering. Another option would be to use the pagemap ptr
> rather than the device ptr as device_private owner, but that would OTOH
> require a wider filtering in hmm_range_fault() so that (or a similar)
> patch would be needed anyway.
>
Yea pagemap group is likely a better device_private_owner. Then I think
we'd drop gpusvm->device_private_owner pointer too which is likely a
good idea anyways.
Matt
> Thanks,
> Thomas
>
> >
> > Matt
> >
> > [1] https://patchwork.freedesktop.org/series/139994/
> >
> > > /Thanks,
> > > Thomas
> > >
>
