On Fri, Jan 17, 2025 at 10:26:16AM +0200, Gwan-gyeong Mun wrote:
>
>
> On 12/18/24 1:33 AM, 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 is largely inspired by GPUVM.
> >
> > v2:
> > - Take order into account in check pages
> > - Clear range->pages in get pages error
> > - Drop setting dirty or accessed bit in get pages (Vetter)
> > - Remove mmap assert for cpu faults
> > - Drop mmap write lock abuse (Vetter, Christian)
> > - Decouple zdd from range (Vetter, Oak)
> > - Add drm_gpusvm_range_evict, make it work with coherent pages
> > - Export drm_gpusvm_evict_to_sram, only use in BO evict path (Vetter)
> > - mmget/put in drm_gpusvm_evict_to_sram
> > - Drop range->vram_alloation variable
> > - Don't return in drm_gpusvm_evict_to_sram until all pages detached
> > - Don't warn on mixing sram and device pages
> > - Update kernel doc
> > - Add coherent page support to get pages
> > - Use DMA_FROM_DEVICE rather than DMA_BIDIRECTIONAL
> > - Add struct drm_gpusvm_vram and ops (Thomas)
> > - Update the range's seqno if the range is valid (Thomas)
> > - Remove the is_unmapped check before hmm_range_fault (Thomas)
> > - Use drm_pagemap (Thomas)
> > - Drop kfree_mapping (Thomas)
> > - dma mapp pages under notifier lock (Thomas)
> > - Remove ctx.prefault
> > - Remove ctx.mmap_locked
> > - Add ctx.check_pages
> > - s/vram/devmem (Thomas)
> > v3:
> > - Fix memory leak drm_gpusvm_range_get_pages
> > - Only migrate pages with same zdd on CPU fault
> > - Loop over al VMAs in drm_gpusvm_range_evict
> > - Make GPUSVM a drm level module
> > - GPL or MIT license
> > - Update main kernel doc (Thomas)
> > - Prefer foo() vs foo for functions in kernel doc (Thomas)
> > - Prefer functions over macros (Thomas)
> > - Use unsigned long vs u64 for addresses (Thomas)
> > - Use standard interval_tree (Thomas)
> > - s/drm_gpusvm_migration_put_page/drm_gpusvm_migration_unlock_put_page (Thomas)
> > - Drop err_out label in drm_gpusvm_range_find_or_insert (Thomas)
> > - Fix kernel doc in drm_gpusvm_range_free_pages (Thomas)
> > - Newlines between functions defs in header file (Thomas)
> > - Drop shall language in driver vfunc kernel doc (Thomas)
> > - Move some static inlines from head to C file (Thomas)
> > - Don't allocate pages under page lock in drm_gpusvm_migrate_populate_ram_pfn (Thomas)
> > - Change check_pages to a threshold
> >
> > Cc: Simona Vetter <simona.vetter@xxxxxxxx>
> > Cc: Dave Airlie <airlied@xxxxxxxxxx>
> > Cc: Christian König <christian.koenig@xxxxxxx>
> > Cc: <dri-devel@xxxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/Kconfig | 8 +
> > drivers/gpu/drm/Makefile | 1 +
> > drivers/gpu/drm/drm_gpusvm.c | 2220 ++++++++++++++++++++++++++++++++++
> > include/drm/drm_gpusvm.h | 445 +++++++
> > 4 files changed, 2674 insertions(+)
> > create mode 100644 drivers/gpu/drm/drm_gpusvm.c
> > create mode 100644 include/drm/drm_gpusvm.h
> >
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > index 2f51546b0b88..5524cb1ed9dd 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -278,6 +278,14 @@ config DRM_GPUVM
> > GPU-VM representation providing helpers to manage a GPUs virtual
> > address space
> > +config DRM_GPUSVM
> > + tristate
> > + depends on DRM
> > + depends on DEVICE_MIGRATION
> > + help
> > + GPU-SVM representation providing helpers to manage a GPUs shared
> > + virtual memory
> > +
> > config DRM_BUDDY
> > tristate
> > depends on DRM
> > diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> > index 19fb370fbc56..ca5d44441fb6 100644
> > --- a/drivers/gpu/drm/Makefile
> > +++ b/drivers/gpu/drm/Makefile
> > @@ -104,6 +104,7 @@ obj-$(CONFIG_DRM_PANEL_BACKLIGHT_QUIRKS) += drm_panel_backlight_quirks.o
> > #
> > obj-$(CONFIG_DRM_EXEC) += drm_exec.o
> > obj-$(CONFIG_DRM_GPUVM) += drm_gpuvm.o
> > +obj-$(CONFIG_DRM_GPUSVM) += drm_gpusvm.o
> > obj-$(CONFIG_DRM_BUDDY) += drm_buddy.o
> > diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
> > new file mode 100644
> > index 000000000000..29ce2c7d1c8c
> > --- /dev/null
> > +++ b/drivers/gpu/drm/drm_gpusvm.c
> > @@ -0,0 +1,2220 @@
> > +// SPDX-License-Identifier: GPL-2.0-only OR MIT
> > +/*
> > + * Copyright © 2024 Intel Corporation
> > + *
> > + * Authors:
> > + * Matthew Brost <matthew.brost@xxxxxxxxx>
> > + */
> > +
> > +#include <linux/dma-mapping.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/drm_gpusvm.h>
> > +#include <drm/drm_pagemap.h>
> > +#include <drm/drm_print.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 GPU SVM operations
> > + * such as range allocation, notifier allocation, and
> > + * invalidations.
> > + * - Device Memory Allocations: Embedded structure containing enough information
> > + * for GPU SVM to migrate to / from device memory.
> > + * - Device Memory Operations: Define the interface for driver-specific device
> > + * memory operations release memory, populate pfns,
> > + * and copy to / from device memory.
> > + *
> > + * 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
> > + * device memory, and create GPU bindings.
> > + * - Garbage collector: Used to unmap and destroy GPU bindings for ranges.
> > + * Ranges are expected to be added to the garbage collector
> > + * upon a MMU_NOTIFY_UNMAP event in notifier callback.
> > + * - Notifier callback: Used to invalidate and DMA unmap GPU bindings for
> > + * ranges.
> > + */
> > +
> > +/**
> > + * DOC: Locking
> > + *
> > + * GPU SVM handles locking for core MM interactions, i.e., it locks/unlocks the
> > + * mmap lock as needed.
> > + *
> > + * 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 range's pages being valid
> > + * (drm_gpusvm_range_pages_valid) 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. This lock is
> > + * denoted as 'driver_svm_lock' in code examples. Finer grained driver side
> > + * locking should also be possible for concurrent GPU fault processing within a
> > + * single GPU SVM. The 'driver_svm_lock' can be via drm_gpusvm_driver_set_lock
> > + * to add annotations to GPU SVM.
> > + */
> > +
> > +/**
> > + * DOC: Migration
> > + *
> > + * The migration support is quite simple, allowing migration between RAM and
> > + * device memory at the range granularity. For example, GPU SVM currently does not
> > + * support mixing RAM and device memory pages within a range. This means that upon GPU
> > + * fault, the entire range can be migrated to device memory, and upon CPU fault, the
> > + * entire range is migrated to RAM. Mixed RAM and device memory storage within a range
> > + * could be added in the future if required.
> > + *
> > + * 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 device memory, a subset of the backing store has
> > + * references. One option would be to split the range and device memory 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 device memory as its backing, the driver is also expected to migrate any
> > + * remaining pages back to RAM.
> > + */
> > +
> > +/**
> > + * DOC: Examples
> > + *
> > + * This section provides three examples of how to build the expected driver
> > + * components: the GPU page fault handler, the garbage collector, and the
> > + * notifier callback.
> > + *
> > + * The generic code provided does not include logic for complex migration
> > + * policies, optimized invalidations, fined grained driver locking, 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, unsigned long fault_addr,
> > + * unsigned long gpuva_start, unsigned long 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)) {
> > + * devmem = driver_alloc_devmem();
> > + * err = drm_gpusvm_migrate_to_devmem(gpusvm, range,
> > + * devmem_allocation,
> > + * &ctx);
> > + * if (err) // CPU mappings may have changed
> > + * goto retry;
> > + * }
> > + *
> > + * err = drm_gpusvm_range_get_pages(gpusvm, range, &ctx);
> > + * if (err == -EOPNOTSUPP || err == -EFAULT || err == -EPERM) { // CPU mappings changed
> > + * if (err == -EOPNOTSUPP)
> > + * drm_gpusvm_range_evict(gpusvm, range);
> > + * 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)
> > + * {
> > + * assert_driver_svm_locked(gpusvm);
> > + *
> > + * // Partial unmap, migrate any remaining device memory pages back to RAM
> > + * if (range->flags.partial_unmap)
> > + * drm_gpusvm_range_evict(gpusvm, range);
> > + *
> > + * 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) Notifier callback.
> > + *
> > + * 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_pages(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);
> > + * }
> > + * }
> > + */
> > +
> > +/**
> > + * 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.
> > + */
> > +static unsigned long
> > +npages_in_range(unsigned long start, unsigned long end)
> > +{
> > + return (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
> > + * @devmem_allocation: device memory allocation
> > + * @device_private_page_owner: Device private pages owner
> > + *
> > + * This structure serves as a generic wrapper installed in
> > + * page->zone_device_data. It provides infrastructure for looking up a device
> > + * memory allocation upon CPU page fault and asynchronously releasing device
> > + * memory once the CPU has no page references. Asynchronous release is useful
> > + * because CPU page references can be dropped in IRQ contexts, while releasing
> > + * device memory likely requires sleeping locks.
> > + */
> > +struct drm_gpusvm_zdd {
> > + struct kref refcount;
> > + struct work_struct destroy_work;
> > + struct drm_gpusvm_devmem *devmem_allocation;
> > + void *device_private_page_owner;
> > +};
> > +
> > +/**
> > + * drm_gpusvm_zdd_destroy_work_func() - Work function for destroying a zdd
> > + * @w: Pointer to the work_struct
> > + *
> > + * This function releases device memory, 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);
> > + const struct drm_gpusvm_devmem_ops *ops = zdd->devmem_allocation ?
> > + zdd->devmem_allocation->ops : NULL;
> > +
> > + if (zdd->devmem_allocation && ops->devmem_release)
> > + ops->devmem_release(zdd->devmem_allocation);
> > + kfree(zdd);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_zdd_alloc() - Allocate a zdd structure.
> > + * @device_private_page_owner: Device private pages owner
> > + *
> > + * This function allocates and initializes a new zdd structure. It sets up the
> > + * reference count and initializes the destroy work.
> > + *
> > + * Returns:
> > + * Pointer to the allocated zdd on success, ERR_PTR() on failure.
> > + */
> > +static struct drm_gpusvm_zdd *
> > +drm_gpusvm_zdd_alloc(void *device_private_page_owner)
> > +{
> > + 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->devmem_allocation = NULL;
> > + zdd->device_private_page_owner = device_private_page_owner;
> > +
> > + 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);
> > +
> > + if (zdd->devmem_allocation)
> > + WRITE_ONCE(zdd->devmem_allocation->detached, true);
> > + schedule_work(&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, unsigned long start,
> > + unsigned long end)
> > +{
> > + struct interval_tree_node *itree;
> > +
> > + itree = interval_tree_iter_first(¬ifier->root, start, end - 1);
> > +
> > + if (itree)
> > + return container_of(itree, struct drm_gpusvm_range, itree);
> > + else
> > + return NULL;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_find);
> > +
> > +/**
> > + * 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__->itree.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->entry,
> > + ¬ifier->gpusvm->notifier_list))
> > + return list_next_entry(notifier, entry);
> > +
> > + return NULL;
> > +}
> > +
> > +static struct drm_gpusvm_notifier *
> > +notifier_iter_first(struct rb_root_cached *root, unsigned long start,
> > + unsigned long last)
> > +{
> > + struct interval_tree_node *itree;
> > +
> > + itree = interval_tree_iter_first(root, start, last);
> > +
> > + if (itree)
> > + return container_of(itree, struct drm_gpusvm_notifier, itree);
> > + else
> > + 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__->itree.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__->itree.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,
> > + unsigned long mm_start, unsigned long mm_range,
> > + unsigned long notifier_size,
> > + const struct drm_gpusvm_ops *ops,
> > + const unsigned long *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;
> > +
> > + 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);
> > +
> > +#ifdef CONFIG_LOCKDEP
> > + gpusvm->lock_dep_map = NULL;
> > +#endif
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_init);
> > +
> > +/**
> > + * drm_gpusvm_notifier_find() - Find GPU SVM notifier
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @fault_addr: Fault address
> > + *
> > + * This function finds the GPU SVM notifier associated with the fault address.
> > + *
> > + * Returns:
> > + * Pointer to the GPU SVM notifier on success, NULL otherwise.
> > + */
> > +static struct drm_gpusvm_notifier *
> > +drm_gpusvm_notifier_find(struct drm_gpusvm *gpusvm,
> > + unsigned long fault_addr)
> > +{
> > + return 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.
> > + */
> > +static struct drm_gpusvm_notifier *to_drm_gpusvm_notifier(struct rb_node *node)
> > +{
> > + return container_of(node, struct drm_gpusvm_notifier, itree.rb);
> > +}
> > +
> > +/**
> > + * 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;
> > +
> > + interval_tree_insert(¬ifier->itree, &gpusvm->root);
> > +
> > + node = rb_prev(¬ifier->itree.rb);
> > + if (node)
> > + head = &(to_drm_gpusvm_notifier(node))->entry;
> > + else
> > + head = &gpusvm->notifier_list;
> > +
> > + list_add(¬ifier->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 function removes the GPU SVM notifier from the GPU SVM RB tree and list.
> > + */
> > +static void drm_gpusvm_notifier_remove(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_notifier *notifier)
> > +{
> > + interval_tree_remove(¬ifier->itree, &gpusvm->root);
> > + list_del(¬ifier->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));
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_fini);
> > +
> > +/**
> > + * 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, unsigned long 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->itree.start = ALIGN_DOWN(fault_addr, gpusvm->notifier_size);
> > + notifier->itree.last = ALIGN(fault_addr + 1, gpusvm->notifier_size) - 1;
> > + INIT_LIST_HEAD(¬ifier->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.
> > + */
> > +static struct drm_gpusvm_range *to_drm_gpusvm_range(struct rb_node *node)
> > +{
> > + return container_of(node, struct drm_gpusvm_range, itree.rb);
> > +}
> > +
> > +/**
> > + * 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);
> > + interval_tree_insert(&range->itree, ¬ifier->root);
> > +
> > + node = rb_prev(&range->itree.rb);
> > + if (node)
> > + head = &(to_drm_gpusvm_range(node))->entry;
> > + else
> > + head = ¬ifier->range_list;
> > +
> > + list_add(&range->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.
> > + */
> > +static void __drm_gpusvm_range_remove(struct drm_gpusvm_notifier *notifier,
> > + struct drm_gpusvm_range *range)
> > +{
> > + interval_tree_remove(&range->itree, ¬ifier->root);
> > + list_del(&range->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_devmem: Flag indicating whether to migrate device memory
> > + *
> > + * 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,
> > + unsigned long fault_addr, unsigned long chunk_size,
> > + bool migrate_devmem)
> > +{
> > + 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->itree.start = ALIGN_DOWN(fault_addr, chunk_size);
> > + range->itree.last = ALIGN(fault_addr + 1, chunk_size) - 1;
> > + INIT_LIST_HEAD(&range->entry);
> > + range->notifier_seq = LONG_MAX;
> > + range->flags.migrate_devmem = migrate_devmem ? 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,
> > + unsigned long start, unsigned long 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;) {
> > + if (!(pfns[i] & HMM_PFN_VALID)) {
> > + err = -EFAULT;
> > + goto err_free;
> > + }
> > + i += 0x1 << hmm_pfn_to_map_order(pfns[i]);
> > + }
> > +
> > +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
> Hi Matthew Brost,
>
> mm core mainly uses vma as the naming of the structure vm_area_struct
> variable.
> can you consider changing vas to vma for the same recognition as mm core?
> ( vas naming is used in this function, as well as many of the functions
> introduced in this patch. )
This is intentional. We are not in core MM rather a GPU driver. GPUs
also have VMAs, grep for vma in DRM subsystem. These are GPU VMAs while
a vm_area_struct is a CPU VMA. To avoid confusing GPU VMAs and CPU VMAs,
I decided on 'vas' for the latter in this code.
> > + * @fault_addr: Fault address
> > + * @gpuva_start: Start address of GPUVA which mirrors CPU
> > + * @gpuva_end: End address of GPUVA which mirrors CPU
> > + * @check_pages_threshold: Check CPU pages for present threshold
> > + *
> > + * 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 unsigned long
> > +drm_gpusvm_range_chunk_size(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_notifier *notifier,
> > + struct vm_area_struct *vas,
> > + unsigned long fault_addr,
> > + unsigned long gpuva_start,
> > + unsigned long gpuva_end,
> > + unsigned long check_pages_threshold)
> > +{
> > + unsigned long 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->itree.start &&
> > + end <= notifier->itree.last + 1 &&
> > + 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_devmem 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 (end - start <= check_pages_threshold &&
> > + !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,
> > + unsigned long fault_addr,
> > + unsigned long gpuva_start,
> > + unsigned long 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;
> > + unsigned long chunk_size;
> > + int err;
> > + bool migrate_devmem;
> > +
> > + drm_gpusvm_driver_lock_held(gpusvm);
> > +
> > + if (fault_addr < gpusvm->mm_start ||
> > + fault_addr > gpusvm->mm_start + gpusvm->mm_range)
> > + return ERR_PTR(-EINVAL);
> > +
> > + if (!mmget_not_zero(mm))
> > + return ERR_PTR(-EFAULT);
> > +
> > + 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(¬ifier->notifier,
> > + mm, notifier->itree.start,
> > + notifier->itree.last -
> > + notifier->itree.start + 1,
> > + &drm_gpusvm_notifier_ops);
> > + if (err)
> > + goto err_notifier;
> > + }
> > +
> > + mmap_read_lock(mm);
> > +
> > + 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_devmem = ctx->devmem_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_devmem &&
> > + ctx->check_pages_threshold);
> > + if (chunk_size == LONG_MAX) {
> > + err = -EINVAL;
> > + goto err_notifier_remove;
> > + }
> > +
> > + range = drm_gpusvm_range_alloc(gpusvm, notifier, fault_addr, chunk_size,
> > + migrate_devmem);
> > + 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);
> > +
> > +out_mmunlock:
> > + mmap_read_unlock(mm);
> > + mmput(mm);
> > +
> > + return range;
> > +
> > +err_notifier_remove:
> > + mmap_read_unlock(mm);
> > + if (notifier_alloc)
> > + mmu_interval_notifier_remove(¬ifier->notifier);
> > +err_notifier:
> > + if (notifier_alloc)
> > + drm_gpusvm_notifier_free(gpusvm, notifier);
> > +err_mmunlock:
> > + mmput(mm);
> > + return ERR_PTR(err);
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_find_or_insert);
> > +
> > +/**
> > + * __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
> > + * @npages: Number of pages to unmap
> > + *
> > + * 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,
> > + unsigned long npages)
> > +{
> > + unsigned long i, j;
> > + struct drm_pagemap *dpagemap = range->dpagemap;
> > + struct device *dev = gpusvm->drm->dev;
> > +
> > + lockdep_assert_held(&gpusvm->notifier_lock);
> > +
> > + if (range->flags.has_dma_mapping) {
> > + for (i = 0, j = 0; i < npages; j++) {
> > + struct drm_pagemap_dma_addr *addr = &range->dma_addr[j];
> > +
> > + if (addr->proto == DRM_INTERCONNECT_SYSTEM)
> > + dma_unmap_page(dev,
> > + addr->addr,
> > + PAGE_SIZE << addr->order,
> > + addr->dir);
> > + else if (dpagemap && dpagemap->ops->unmap_dma)
> > + dpagemap->ops->unmap_dma(dpagemap,
> > + dev,
> > + *addr);
> > + i += 1 << addr->order;
> > + }
> > + range->flags.has_devmem_pages = false;
> > + range->flags.has_dma_mapping = false;
> > + range->dpagemap = NULL;
> > + }
> > +}
> > +
> > +/**
> > + * 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 frees the dma address array 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->dma_addr) {
> > + kvfree(range->dma_addr);
> > + range->dma_addr = 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)
> > +{
> > + unsigned long npages = npages_in_range(range->itree.start,
> > + range->itree.last + 1);
> > + struct drm_gpusvm_notifier *notifier;
> > +
> > + drm_gpusvm_driver_lock_held(gpusvm);
> > +
> > + notifier = drm_gpusvm_notifier_find(gpusvm, range->itree.start);
> > + if (WARN_ON_ONCE(!notifier))
> > + return;
> > +
> > + drm_gpusvm_notifier_lock(gpusvm);
> > + __drm_gpusvm_range_unmap_pages(gpusvm, range, npages);
> > + 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);
> > + }
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_remove);
> > +
> > +/**
> > + * 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;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_get);
> > +
> > +/**
> > + * 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);
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_put);
> > +
> > +/**
> > + * 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 committing a
> > + * GPU binding. This is akin to a notifier seqno check in the HMM documentation
> > + * but due to wider notifiers (i.e., notifiers which span multiple ranges) this
> > + * function is required for finer grained checking (i.e., per range) if pages
> > + * are valid.
> > + *
> > + * 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_devmem_pages || range->flags.has_dma_mapping;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_pages_valid);
> > +
> > +/**
> > + * 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->dma_addr)
> > + return false;
> > +
> > + drm_gpusvm_notifier_lock(gpusvm);
> > + pages_valid = drm_gpusvm_range_pages_valid(gpusvm, range);
> > + if (!pages_valid)
> > + drm_gpusvm_range_free_pages(gpusvm, range);
> > + 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->itree.start,
> > + .end = range->itree.last + 1,
> > + .dev_private_owner = gpusvm->device_private_page_owner,
> > + };
> > + struct mm_struct *mm = gpusvm->mm;
> > + struct drm_gpusvm_zdd *zdd;
> > + unsigned long timeout =
> > + jiffies + msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> > + unsigned long i, j;
> > + unsigned long npages = npages_in_range(range->itree.start,
> > + range->itree.last + 1);
> > + unsigned long num_dma_mapped;
> > + unsigned int order = 0;
> > + unsigned long *pfns;
> > + struct page **pages;
> > + int err = 0;
> > + struct dev_pagemap *pagemap;
> > + struct drm_pagemap *dpagemap;
> > +
> > +retry:
> > + hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
> > + if (drm_gpusvm_range_pages_valid_unlocked(gpusvm, range))
> > + goto set_seqno;
> > +
> > + pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
> > + if (!pfns)
> > + return -ENOMEM;
> > +
> > + if (!mmget_not_zero(mm)) {
> > + err = -EFAULT;
> > + goto err_free;
> > + }
> > +
> > + hmm_range.hmm_pfns = pfns;
> > + while (true) {
> > + mmap_read_lock(mm);
> > + err = hmm_range_fault(&hmm_range);
> > + mmap_read_unlock(mm);
> > +
> > + if (err == -EBUSY) {
> > + if (time_after(jiffies, timeout))
> > + break;
> > +
> > + hmm_range.notifier_seq = mmu_interval_read_begin(notifier);
> > + continue;
> > + }
> > + break;
> > + }
> > + mmput(mm);
> > + if (err)
> > + goto err_free;
> > +
> > + pages = (struct page **)pfns;
> > +map_pages:
> > + /*
> > + * Perform all dma mappings under the notifier lock to not
> > + * access freed pages. A notifier will either block on
> > + * the notifier lock or unmap dma.
> > + */
> > + drm_gpusvm_notifier_lock(gpusvm);
> > + if (mmu_interval_read_retry(notifier, hmm_range.notifier_seq)) {
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > + kvfree(pfns);
> > + goto retry;
> > + }
> > +
> > + if (!range->dma_addr) {
> > + /* Unlock and restart mapping to allocate memory. */
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > + range->dma_addr = kvmalloc_array(npages, sizeof(*range->dma_addr),
> > + GFP_KERNEL);
> > + if (!range->dma_addr) {
> > + err = -ENOMEM;
> > + goto err_free;
> > + }
> > + goto map_pages;
> > + }
> > +
> > + zdd = NULL;
> > + num_dma_mapped = 0;
> > + for (i = 0, j = 0; i < npages; ++j) {
> > + struct page *page = hmm_pfn_to_page(pfns[i]);
> > +
> > + order = hmm_pfn_to_map_order(pfns[i]);
> > + if (is_device_private_page(page) || is_device_coherent_page(page)) {
> > + if (zdd != page->zone_device_data && i > 0) {
> > + err = -EOPNOTSUPP;
> > + goto err_unmap;
> > + }
> > + zdd = page->zone_device_data;
> > + if (pagemap != page->pgmap) {
> > + if (i > 0) {
> > + err = -EOPNOTSUPP;
> > + goto err_unmap;
> > + }
> > +
> > + pagemap = page->pgmap;
> > + dpagemap = zdd->devmem_allocation->dpagemap;
> > + if (drm_WARN_ON(gpusvm->drm, !dpagemap)) {
> > + /*
> > + * Raced. This is not supposed to happen
> > + * since hmm_range_fault() should've migrated
> > + * this page to system.
> > + */
> > + err = -EAGAIN;
> > + goto err_unmap;
> > + }
> > + }
> > + range->dma_addr[j] =
> > + dpagemap->ops->map_dma(dpagemap, gpusvm->drm->dev,
> > + page, order,
> > + DMA_BIDIRECTIONAL);
> > + if (dma_mapping_error(gpusvm->drm->dev, range->dma_addr[j].addr)) {
> > + err = -EFAULT;
> > + goto err_unmap;
> > + }
> > +
> > + pages[i] = page;
> > + } else {
> > + dma_addr_t addr;
> > +
> > + if (is_zone_device_page(page) || zdd) {
> > + err = -EOPNOTSUPP;
> > + goto err_unmap;
> > + }
> > +
> > + addr = dma_map_page(gpusvm->drm->dev,
> > + page, 0,
> > + PAGE_SIZE << order,
> > + DMA_BIDIRECTIONAL);
> > + if (dma_mapping_error(gpusvm->drm->dev, addr)) {
> > + err = -EFAULT;
> > + goto err_unmap;
> > + }
> > +
> > + range->dma_addr[j] = drm_pagemap_dma_addr_encode
> > + (addr, DRM_INTERCONNECT_SYSTEM, order,
> > + DMA_BIDIRECTIONAL);
> > + }
> > + i += 1 << order;
> > + num_dma_mapped = i;
> > + }
> > +
> > + range->flags.has_dma_mapping = true;
> > + if (zdd) {
> > + range->flags.has_devmem_pages = true;
> > + range->dpagemap = dpagemap;
> > + }
> > +
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > + kvfree(pfns);
> > +set_seqno:
> > + range->notifier_seq = hmm_range.notifier_seq;
> > +
> > + return 0;
> > +
> > +err_unmap:
> > + __drm_gpusvm_range_unmap_pages(gpusvm, range, num_dma_mapped);
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > +err_free:
> > + kvfree(pfns);
> > + if (err == -EAGAIN)
> > + goto retry;
> > + return err;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_get_pages);
> > +
> > +/**
> > + * 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)
> > +{
> > + unsigned long npages = npages_in_range(range->itree.start,
> > + range->itree.last + 1);
> > +
> > + if (ctx->in_notifier)
> > + lockdep_assert_held_write(&gpusvm->notifier_lock);
> > + else
> > + drm_gpusvm_notifier_lock(gpusvm);
> > +
> > + __drm_gpusvm_range_unmap_pages(gpusvm, range, npages);
> > +
> > + if (!ctx->in_notifier)
> > + drm_gpusvm_notifier_unlock(gpusvm);
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_unmap_pages);
> > +
> > +/**
> > + * drm_gpusvm_migration_unlock_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_unlock_put_page(struct page *page)
> > +{
> > + unlock_page(page);
> > + put_page(page);
> > +}
> > +
> > +/**
> > + * drm_gpusvm_migration_unlock_put_pages() - Put migration pages
> > + * @npages: Number of pages
> > + * @migrate_pfn: Array of migrate page frame numbers
> > + *
> > + * This function unlocks and puts an array of pages.
> > + */
> > +static void drm_gpusvm_migration_unlock_put_pages(unsigned long npages,
> > + unsigned long *migrate_pfn)
> > +{
> > + unsigned long i;
> > +
> > + for (i = 0; i < npages; ++i) {
> > + struct page *page;
> > +
> > + if (!migrate_pfn[i])
> > + continue;
> > +
> > + page = migrate_pfn_to_page(migrate_pfn[i]);
> > + drm_gpusvm_migration_unlock_put_page(page);
> > + migrate_pfn[i] = 0;
> > + }
> > +}
> > +
> > +/**
> > + * drm_gpusvm_get_devmem_page() - Get a reference to a device memory 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_devmem_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,
> > + unsigned long *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_devmem() - Migrate GPU SVM range to device memory
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range structure
> > + * @devmem_allocation: Pointer to the device memory allocation. The caller
> > + * should hold a reference to the device memory allocation,
> > + * which should be dropped via ops->devmem_release or upon
> > + * the failure of this function.
> > + * @ctx: GPU SVM context
> > + *
> > + * This function migrates the specified GPU SVM range to device memory. It performs the
> > + * necessary setup and invokes the driver-specific operations for migration to
> > + * device memory. Upon successful return, @devmem_allocation can safely reference @range
> > + * until ops->devmem_release is called which only upon successful return.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +int drm_gpusvm_migrate_to_devmem(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range,
> > + struct drm_gpusvm_devmem *devmem_allocation,
> > + const struct drm_gpusvm_ctx *ctx)
> > +{
> > + const struct drm_gpusvm_devmem_ops *ops = devmem_allocation->ops;
> > + unsigned long start = range->itree.start, end = range->itree.last + 1;
> > + 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_devmem)
> > + return -EINVAL;
> > +
> > + if (!ops->populate_devmem_pfn || !ops->copy_to_devmem ||
> > + !ops->copy_to_ram)
> > + return -EOPNOTSUPP;
> > +
> > + if (!mmget_not_zero(mm)) {
> > + err = -EFAULT;
> > + goto err_out;
> > + }
> > + mmap_read_lock(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(gpusvm->device_private_page_owner);
> > + 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;
> > +
> > + if (!migrate.cpages) {
> > + err = -EFAULT;
> > + goto err_free;
> > + }
> > +
> > + if (migrate.cpages != npages) {
> > + err = -EBUSY;
> > + goto err_finalize;
> > + }
> > +
> > + err = ops->populate_devmem_pfn(devmem_allocation, npages, migrate.dst);
> > + if (err)
> > + goto err_finalize;
> > +
> > + err = drm_gpusvm_migrate_map_pages(devmem_allocation->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_devmem_page(page, zdd);
> > + }
> > +
> > + err = ops->copy_to_devmem(pages, dma_addr, npages);
> > + if (err)
> > + goto err_finalize;
> > +
> > + /* Upon success bind devmem allocation to range and zdd */
> > + WRITE_ONCE(zdd->devmem_allocation, devmem_allocation); /* Owns ref */
> > +
> > +err_finalize:
> > + if (err)
> > + drm_gpusvm_migration_unlock_put_pages(npages, migrate.dst);
> > + migrate_vma_pages(&migrate);
> > + migrate_vma_finalize(&migrate);
> > + drm_gpusvm_migrate_unmap_pages(devmem_allocation->dev, dma_addr, npages,
> > + DMA_TO_DEVICE);
> > +err_free:
> > + if (zdd)
> > + drm_gpusvm_zdd_put(zdd);
> > + kvfree(buf);
> > +err_mmunlock:
> > + mmap_read_unlock(mm);
> > + mmput(mm);
> > +err_out:
> > + return err;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_migrate_to_devmem);
> > +
> > +/**
> > + * drm_gpusvm_migrate_populate_ram_pfn() - Populate RAM PFNs for a VM area
> > + * @vas: Pointer to the VM area structure, can be NULL
> > + * @fault_page: Fault page
> > + * @npages: Number of pages to populate
> > + * @mpages: Number of pages to migrate
> > + * @src_mpfn: Source array of migrate PFNs
> > + * @mpfn: Array of migrate PFNs to populate
> > + * @addr: Start address for PFN allocation
> > + *
> > + * This function populates the RAM migrate page frame numbers (PFNs) for the
> > + * specified VM area structure. It allocates and locks pages in the VM area for
> > + * RAM 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_ram_pfn(struct vm_area_struct *vas,
> > + struct page *fault_page,
> > + unsigned long npages,
> > + unsigned long *mpages,
> > + unsigned long *src_mpfn,
> > + unsigned long *mpfn,
> > + unsigned long addr)
> > +{
> > + unsigned long i;
> > +
> > + for (i = 0; i < npages; ++i, addr += PAGE_SIZE) {
> > + struct page *page, *src_page;
> > +
> > + if (!(src_mpfn[i] & MIGRATE_PFN_MIGRATE))
> > + continue;
> > +
> > + if (fault_page) {
> > + src_page = migrate_pfn_to_page(src_mpfn[i]);
> > + if (src_page->zone_device_data !=
> > + fault_page->zone_device_data)
> > + continue;
> > + }
> > +
> > + if (vas)
> > + page = alloc_page_vma(GFP_HIGHUSER, vas, addr);
> > + else
> > + page = alloc_page(GFP_HIGHUSER);
> > +
> > + if (!page)
> > + goto free_pages;
> > +
> > + mpfn[i] = migrate_pfn(page_to_pfn(page));
> > + }
> > +
> > + for (i = 0; i < npages; ++i) {
> > + struct page *page = migrate_pfn_to_page(mpfn[i]);
> > +
> > + if (!page)
> > + continue;
> > +
> > + WARN_ON_ONCE(!trylock_page(page));
> > + ++*mpages;
> > + }
> > +
> > + return 0;
> > +
> > +free_pages:
> > + for (i = 0; i < npages; ++i) {
> > + struct page *page = migrate_pfn_to_page(mpfn[i]);
> > +
> > + if (!page)
> > + continue;
> > +
> > + put_page(page);
> > + mpfn[i] = 0;
> > + }
> > + return -ENOMEM;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_evict_to_ram() - Evict GPU SVM range to RAM
> > + * @devmem_allocation: Pointer to the device memory allocation
> > + *
> > + * Similar to __drm_gpusvm_migrate_to_ram but does not require mmap lock and
> > + * migration done via migrate_device_* functions.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +int drm_gpusvm_evict_to_ram(struct drm_gpusvm_devmem *devmem_allocation)
> > +{
> > + const struct drm_gpusvm_devmem_ops *ops = devmem_allocation->ops;
> > + unsigned long npages, mpages = 0;
> > + struct page **pages;
> > + unsigned long *src, *dst;
> > + dma_addr_t *dma_addr;
> > + void *buf;
> > + int i, err = 0;
> > +
> > + npages = devmem_allocation->size >> PAGE_SHIFT;
> > +
> > +retry:
> > + if (!mmget_not_zero(devmem_allocation->mm))
> > + return -EFAULT;
> > +
> > + 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 = ops->populate_devmem_pfn(devmem_allocation, npages, src);
> > + if (err)
> > + goto err_free;
> > +
> > + err = migrate_device_pfns(src, npages);
> > + if (err)
> > + goto err_free;
> > +
> > + err = drm_gpusvm_migrate_populate_ram_pfn(NULL, NULL, npages, &mpages,
> > + src, dst, 0);
> > + if (err || !mpages)
> > + goto err_finalize;
> > +
> > + err = drm_gpusvm_migrate_map_pages(devmem_allocation->dev, dma_addr,
> > + dst, npages, DMA_FROM_DEVICE);
> > + if (err)
> > + goto err_finalize;
> > +
> > + for (i = 0; i < npages; ++i)
> > + pages[i] = migrate_pfn_to_page(src[i]);
> > +
> > + err = ops->copy_to_ram(pages, dma_addr, npages);
> > + if (err)
> > + goto err_finalize;
> > +
> > +err_finalize:
> > + if (err)
> > + drm_gpusvm_migration_unlock_put_pages(npages, dst);
> > + migrate_device_pages(src, dst, npages);
> > + migrate_device_finalize(src, dst, npages);
> > + drm_gpusvm_migrate_unmap_pages(devmem_allocation->dev, dma_addr, npages,
> > + DMA_FROM_DEVICE);
> > +err_free:
> > + kvfree(buf);
> > +err_out:
> > + mmput_async(devmem_allocation->mm);
> > + if (!err && !READ_ONCE(devmem_allocation->detached)) {
> > + cond_resched();
> > + goto retry;
> > + }
> > +
> > + return err;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_evict_to_ram);
> > +
> > +/**
> > + * __drm_gpusvm_migrate_to_ram() - Migrate GPU SVM range to RAM (internal)
> > + * @vas: Pointer to the VM area structure
> > + * @device_private_page_owner: Device private pages owner
> > + * @page: Pointer to the page for fault handling (can be NULL)
> > + * @fault_addr: Fault address
> > + * @size: Size of migration
> > + *
> > + * This internal function performs the migration of the specified GPU SVM range
> > + * to RAM. It sets up the migration, populates + dma maps RAM PFNs, and
> > + * invokes the driver-specific operations for migration to RAM.
> > + *
> > + * Returns:
> > + * 0 on success, negative error code on failure.
> > + */
> > +static int __drm_gpusvm_migrate_to_ram(struct vm_area_struct *vas,
> > + void *device_private_page_owner,
> > + struct page *page,
> > + unsigned long fault_addr,
> > + unsigned long size)
> > +{
> > + struct migrate_vma migrate = {
> > + .vma = vas,
> > + .pgmap_owner = device_private_page_owner,
> > + .flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE |
> > + MIGRATE_VMA_SELECT_DEVICE_COHERENT,
> > + .fault_page = page,
> > + };
> > + struct drm_gpusvm_zdd *zdd;
> > + const struct drm_gpusvm_devmem_ops *ops;
> > + struct device *dev;
> > + unsigned long npages, mpages = 0;
> > + struct page **pages;
> > + dma_addr_t *dma_addr;
> > + unsigned long start, end;
> > + void *buf;
> > + int i, err = 0;
> > +
> > + start = ALIGN_DOWN(fault_addr, size);
> > + end = ALIGN(fault_addr + 1, size);
> > +
> > + /* 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;
> > +
> > + if (!page) {
> > + for (i = 0; i < npages; ++i) {
> > + if (!(migrate.src[i] & MIGRATE_PFN_MIGRATE))
> > + continue;
> > +
> > + page = migrate_pfn_to_page(migrate.src[i]);
> > + break;
> > + }
> > +
> > + if (!page)
> > + goto err_finalize;
> If you goto to err_finalize through this error case, the uninitialized dev
> will be passed to drm_gpusvm_migrate_unmap_pages().
>
Yep. The code works as drm_gpusvm_migrate_unmap_pages loops over the dma
mappings which will not exist. I suppose I could short circuit this on
if (dev) if you prefer.
Matt
> Br,
> G.G.
> > + }
> > + zdd = page->zone_device_data;
> > + ops = zdd->devmem_allocation->ops;
> > + dev = zdd->devmem_allocation->dev;
> > +
> > + err = drm_gpusvm_migrate_populate_ram_pfn(vas, page, npages, &mpages,
> > + migrate.src, migrate.dst,
> > + start);
> > + if (err)
> > + goto err_finalize;
> > +
> > + err = drm_gpusvm_migrate_map_pages(dev, dma_addr, migrate.dst, npages,
> > + DMA_FROM_DEVICE);
> > + if (err)
> > + goto err_finalize;
> > +
> > + for (i = 0; i < npages; ++i)
> > + pages[i] = migrate_pfn_to_page(migrate.src[i]);
> > +
> > + err = ops->copy_to_ram(pages, dma_addr, npages);
> > + if (err)
> > + goto err_finalize;
> > +
> > +err_finalize:
> > + if (err)
> > + drm_gpusvm_migration_unlock_put_pages(npages, migrate.dst);
> > + migrate_vma_pages(&migrate);
> > + migrate_vma_finalize(&migrate);
> > + drm_gpusvm_migrate_unmap_pages(dev, dma_addr, npages,
> > + DMA_FROM_DEVICE);
> > +err_free:
> > + kvfree(buf);
> > +err_out:
> > +
> > + return err;
> > +}
> > +
> > +/**
> > + * drm_gpusvm_range_evict() - Evict GPU SVM range
> > + * @gpusvm: Pointer to the GPU SVM structure
> > + * @range: Pointer to the GPU SVM range to be removed
> > + *
> > + * This function evicts the specified GPU SVM range.
> > + */
> > +void drm_gpusvm_range_evict(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range)
> > +{
> > + struct mm_struct *mm = gpusvm->mm;
> > + struct vm_area_struct *vas;
> > + unsigned long start = range->itree.start, end = range->itree.last + 1;
> > +
> > + if (!mmget_not_zero(mm))
> > + return;
> > +
> > + mmap_read_lock(mm);
> > +
> > + /*
> > + * Loop required to find all VMAs for the corner case when partial
> > + * unmappings have occurred.
> > + */
> > +again:
> > + vas = find_vma(mm, start);
> > + if (!vas)
> > + goto unlock;
> > +
> > + if (end <= vas->vm_start || start >= vas->vm_end)
> > + goto unlock;
> > +
> > + __drm_gpusvm_migrate_to_ram(vas, gpusvm->device_private_page_owner,
> > + NULL, start,
> > + range->itree.last - range->itree.start + 1);
> > + if (vas->vm_end < end) {
> > + start = vas->vm_end;
> > + goto again;
> > + }
> > +unlock:
> > + mmap_read_unlock(mm);
> > + mmput(mm);
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_evict);
> > +
> > +/**
> > + * 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_ram(vmf->vma,
> > + zdd->device_private_page_owner,
> > + vmf->page, vmf->address,
> > + zdd->devmem_allocation->size);
> > +
> > + 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;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_pagemap_ops_get);
> > +
> > +/**
> > + * 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, unsigned long start,
> > + unsigned long 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;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_has_mapping);
> > +
> > +/**
> > + * 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.
> > + */
> > +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->itree.start < mmu_range->start ||
> > + range->itree.last + 1 > mmu_range->end)
> > + range->flags.partial_unmap = true;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_range_set_unmapped);
> > +
> > +/**
> > + * drm_gpusvm_devmem_init() - Initialize a GPU SVM device memory allocation
> > + *
> > + * @dev: Pointer to the device structure which device memory allocation belongs to
> > + * @mm: Pointer to the mm_struct for the address space
> > + * @ops: Pointer to the operations structure for GPU SVM device memory
> > + * @dpagemap: The struct drm_pagemap we're allocating from.
> > + * @size: Size of device memory allocation
> > + */
> > +void drm_gpusvm_devmem_init(struct drm_gpusvm_devmem *devmem_allocation,
> > + struct device *dev, struct mm_struct *mm,
> > + const struct drm_gpusvm_devmem_ops *ops,
> > + struct drm_pagemap *dpagemap, size_t size)
> > +{
> > + devmem_allocation->dev = dev;
> > + devmem_allocation->mm = mm;
> > + devmem_allocation->ops = ops;
> > + devmem_allocation->dpagemap = dpagemap;
> > + devmem_allocation->size = size;
> > +}
> > +EXPORT_SYMBOL_GPL(drm_gpusvm_devmem_init);
> > +
> > +MODULE_DESCRIPTION("DRM GPUSVM");
> > +MODULE_LICENSE("GPL");
> > diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h
> > new file mode 100644
> > index 000000000000..2fb6980d0cf1
> > --- /dev/null
> > +++ b/include/drm/drm_gpusvm.h
> > @@ -0,0 +1,445 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
> > +/*
> > + * Copyright © 2024 Intel Corporation
> > + */
> > +
> > +#ifndef __DRM_GPUSVM_H__
> > +#define __DRM_GPUSVM_H__
> > +
> > +#include <linux/kref.h>
> > +#include <linux/interval_tree.h>
> > +#include <linux/mmu_notifier.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_devmem;
> > +struct drm_pagemap;
> > +struct drm_pagemap_dma_addr;
> > +
> > +/**
> > + * struct drm_gpusvm_devmem_ops - Operations structure for GPU SVM device memory
> > + *
> > + * This structure defines the operations for GPU Shared Virtual Memory (SVM)
> > + * device memory. These operations are provided by the GPU driver to manage device memory
> > + * allocations and perform operations such as migration between device memory and system
> > + * RAM.
> > + */
> > +struct drm_gpusvm_devmem_ops {
> > + /**
> > + * @devmem_release: Release device memory allocation (optional)
> > + * @devmem_allocation: device memory allocation
> > + *
> > + * Release device memory allocation and drop a reference to device
> > + * memory allocation.
> > + */
> > + void (*devmem_release)(struct drm_gpusvm_devmem *devmem_allocation);
> > +
> > + /**
> > + * @populate_devmem_pfn: Populate device memory PFN (required for migration)
> > + * @devmem_allocation: device memory allocation
> > + * @npages: Number of pages to populate
> > + * @pfn: Array of page frame numbers to populate
> > + *
> > + * Populate device memory page frame numbers (PFN).
> > + *
> > + * Returns:
> > + * 0 on success, a negative error code on failure.
> > + */
> > + int (*populate_devmem_pfn)(struct drm_gpusvm_devmem *devmem_allocation,
> > + unsigned long npages, unsigned long *pfn);
> > +
> > + /**
> > + * @copy_to_devmem: Copy to device memory (required for migration)
> > + * @pages: Pointer to array of device memory pages (destination)
> > + * @dma_addr: Pointer to array of DMA addresses (source)
> > + * @npages: Number of pages to copy
> > + *
> > + * Copy pages to device memory.
> > + *
> > + * Returns:
> > + * 0 on success, a negative error code on failure.
> > + */
> > + int (*copy_to_devmem)(struct page **pages,
> > + dma_addr_t *dma_addr,
> > + unsigned long npages);
> > +
> > + /**
> > + * @copy_to_ram: Copy to system RAM (required for migration)
> > + * @pages: Pointer to array of device memory pages (source)
> > + * @dma_addr: Pointer to array of DMA addresses (destination)
> > + * @npages: Number of pages to copy
> > + *
> > + * Copy pages to system RAM.
> > + *
> > + * Returns:
> > + * 0 on success, a negative error code on failure.
> > + */
> > + int (*copy_to_ram)(struct page **pages,
> > + dma_addr_t *dma_addr,
> > + unsigned long npages);
> > +};
> > +
> > +/**
> > + * struct drm_gpusvm_devmem - Structure representing a GPU SVM device memory allocation
> > + *
> > + * @dev: Pointer to the device structure which device memory allocation belongs to
> > + * @mm: Pointer to the mm_struct for the address space
> > + * @ops: Pointer to the operations structure for GPU SVM device memory
> > + * @dpagemap: The struct drm_pagemap of the pages this allocation belongs to.
> > + * @size: Size of device memory allocation
> > + * @detached: device memory allocations is detached from device pages
> > + */
> > +struct drm_gpusvm_devmem {
> > + struct device *dev;
> > + struct mm_struct *mm;
> > + const struct drm_gpusvm_devmem_ops *ops;
> > + struct drm_pagemap *dpagemap;
> > + size_t size;
> > + bool detached;
> > +};
> > +
> > +/**
> > + * 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
> > + * notifiers.
> > + */
> > +struct drm_gpusvm_ops {
> > + /**
> > + * @notifier_alloc: Allocate a GPU SVM notifier (optional)
> > + *
> > + * 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
> > + *
> > + * 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
> > + *
> > + * 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
> > + *
> > + * Free a GPU SVM range.
> > + */
> > + void (*range_free)(struct drm_gpusvm_range *range);
> > +
> > + /**
> > + * @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
> > + *
> > + * 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
> > + * @itree: Interval tree node for the notifier (inserted in GPU SVM)
> > + * @entry: List entry to fast interval tree traversal
> > + * @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 interval_tree_node itree;
> > + struct list_head entry;
> > + 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
> > + * @itree: Interval tree node for the range (inserted in GPU SVM notifier)
> > + * @entry: List entry to fast interval tree traversal
> > + * @notifier_seq: Notifier sequence number of the range's pages
> > + * @dma_addr: DMA address array
> > + * @dpagemap: The struct drm_pagemap of the device pages we're dma-mapping.
> > + * Note this is assuming only one drm_pagemap per range is allowed.
> > + * @flags.migrate_devmem: Flag indicating whether the range can be migrated to device memory
> > + * @flags.unmapped: Flag indicating if the range has been unmapped
> > + * @flags.partial_unmap: Flag indicating if the range has been partially unmapped
> > + * @flags.has_devmem_pages: Flag indicating if the range has devmem pages
> > + * @flags.has_dma_mapping: Flag indicating if the range has a DMA mapping
> > + *
> > + * 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 interval_tree_node itree;
> > + struct list_head entry;
> > + unsigned long notifier_seq;
> > + struct drm_pagemap_dma_addr *dma_addr;
> > + struct drm_pagemap *dpagemap;
> > + struct {
> > + /* All flags below must be set upon creation */
> > + u16 migrate_devmem : 1;
> > + /* All flags below must be set / cleared under notifier lock */
> > + u16 unmapped : 1;
> > + u16 partial_unmap : 1;
> > + u16 has_devmem_pages : 1;
> > + u16 has_dma_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
> > + * @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;
> > + unsigned long mm_start;
> > + unsigned long mm_range;
> > + unsigned long notifier_size;
> > + const struct drm_gpusvm_ops *ops;
> > + const unsigned long *chunk_sizes;
> > + int num_chunks;
> > + struct rw_semaphore notifier_lock;
> > + struct rb_root_cached root;
> > + struct list_head notifier_list;
> > +#ifdef CONFIG_LOCKDEP
> > + /**
> > + * @lock_dep_map: Annotates drm_gpusvm_range_find_or_insert and
> > + * drm_gpusvm_range_remove with a driver provided lock.
> > + */
> > + struct lockdep_map *lock_dep_map;
> > +#endif
> > +};
> > +
> > +/**
> > + * struct drm_gpusvm_ctx - DRM GPU SVM context
> > + *
> > + * @check_pages_threshold: Check CPU pages for present if chunk is less than or
> > + * equal to threshold. If not present, reduce chunk
> > + * size.
> > + * @in_notifier: entering from a MMU notifier
> > + * @read_only: operating on read-only memory
> > + * @devmem_possible: possible to use device memory
> > + *
> > + * Context that is DRM GPUSVM is operating in (i.e. user arguments).
> > + */
> > +struct drm_gpusvm_ctx {
> > + unsigned long check_pages_threshold;
> > + unsigned int in_notifier :1;
> > + unsigned int read_only :1;
> > + unsigned int devmem_possible :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,
> > + unsigned long mm_start, unsigned long mm_range,
> > + unsigned long notifier_size,
> > + const struct drm_gpusvm_ops *ops,
> > + const unsigned long *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,
> > + unsigned long fault_addr,
> > + unsigned long gpuva_start,
> > + unsigned long gpuva_end,
> > + const struct drm_gpusvm_ctx *ctx);
> > +
> > +void drm_gpusvm_range_remove(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range);
> > +
> > +void drm_gpusvm_range_evict(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_devmem(struct drm_gpusvm *gpusvm,
> > + struct drm_gpusvm_range *range,
> > + struct drm_gpusvm_devmem *devmem_allocation,
> > + const struct drm_gpusvm_ctx *ctx);
> > +
> > +int drm_gpusvm_evict_to_ram(struct drm_gpusvm_devmem *devmem_allocation);
> > +
> > +const struct dev_pagemap_ops *drm_gpusvm_pagemap_ops_get(void);
> > +
> > +bool drm_gpusvm_has_mapping(struct drm_gpusvm *gpusvm, unsigned long start,
> > + unsigned long end);
> > +
> > +struct drm_gpusvm_range *
> > +drm_gpusvm_range_find(struct drm_gpusvm_notifier *notifier, unsigned long start,
> > + unsigned long end);
> > +
> > +void drm_gpusvm_range_set_unmapped(struct drm_gpusvm_range *range,
> > + const struct mmu_notifier_range *mmu_range);
> > +
> > +void drm_gpusvm_devmem_init(struct drm_gpusvm_devmem *devmem_allocation,
> > + struct device *dev, struct mm_struct *mm,
> > + const struct drm_gpusvm_devmem_ops *ops,
> > + struct drm_pagemap *dpagemap, size_t size);
> > +
> > +#ifdef CONFIG_LOCKDEP
> > +/**
> > + * drm_gpusvm_driver_set_lock() - Set the lock protecting accesses to GPU SVM
> > + * @gpusvm: Pointer to the GPU SVM structure.
> > + * @lock: the lock used to protect the gpuva list. The locking primitive
> > + * must contain a dep_map field.
> > + *
> > + * Call this to annotate drm_gpusvm_range_find_or_insert and
> > + * drm_gpusvm_range_remove.
> > + */
> > +#define drm_gpusvm_driver_set_lock(gpusvm, lock) \
> > + do { \
> > + if (!WARN((gpusvm)->lock_dep_map, \
> > + "GPUSVM range lock should be set only once."))\
> > + (gpusvm)->lock_dep_map = &(lock)->dep_map; \
> > + } while (0)
> > +#define drm_gpusvm_driver_lock_held(gpusvm) \
> > + do { \
> > + if ((gpusvm)->lock_dep_map) \
> > + lock_is_held((gpusvm)->lock_dep_map); \
> > + } while (0)
> > +#else
> > +#define drm_gpusvm_driver_set_lock(gpusvm, lock) do {} while (0)
> > +#define drm_gpusvm_driver_lock_held(gpusvm) do {} while (0)
> > +#endif
> > +
> > +/**
> > + * 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->entry,
> > + &range->notifier->range_list))
> > + return list_next_entry(range, 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__->itree.start < (end__)); \
> > + (range__) = __drm_gpusvm_range_next(range__))
> > +
> > +#endif /* __DRM_GPUSVM_H__ */
>
