On Tue, 2024-10-15 at 20:24 -0700, Matthew Brost wrote:
Continued review.
>
> +/**
> + * 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
NIT: Even if the above kerneldoc format works, I keep trying to enforce
using () after function names and function-like macros, like described
here: https://docs.kernel.org/doc-guide/kernel-doc.html Could we
update? Also that doc calls for using "Return:" instead of "Returns:".
> + * @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);
> +}
As mentioned earlier, I think the above drm_gpusvm_zdd functions should
move to drm_pagemap.c. I don't think they are used in drm_gpusvm other
than to, at get_pages time, ensure all device private pages are from
the same pagemap?
> +
> +/**
> + * drm_gpusvm_range_find - Find GPU SVM range from GPU SVM notifier
> + * @notifier: Pointer to the GPU SVM notifier structure.
> + * @start: Start address of the range
> + * @end: End address of the range
> + *
> + * Return: A pointer to the drm_gpusvm_range if found or NULL
> + */
> +struct drm_gpusvm_range *
> +drm_gpusvm_range_find(struct drm_gpusvm_notifier *notifier, u64
> start, u64 end)
> +{
> + return range_iter_first(¬ifier->root, start, end - 1);
> +}
> +
> +/**
> + * drm_gpusvm_for_each_range_safe - Safely iterate over GPU SVM
> ranges in a notifier
> + * @range__: Iterator variable for the ranges
> + * @next__: Iterator variable for the ranges temporay storage
> + * @notifier__: Pointer to the GPU SVM notifier
> + * @start__: Start address of the range
> + * @end__: End address of the range
> + *
> + * This macro is used to iterate over GPU SVM ranges in a notifier
> while
> + * removing ranges from it.
> + */
> +#define drm_gpusvm_for_each_range_safe(range__, next__, notifier__,
> start__, end__) \
> + for ((range__) = drm_gpusvm_range_find((notifier__),
> (start__), (end__)), \
> + (next__) =
> __drm_gpusvm_range_next(range__); \
> + (range__) && (range__->va.start <
> (end__)); \
> + (range__) = (next__), (next__) =
> __drm_gpusvm_range_next(range__))
> +
> +/**
> + * __drm_gpusvm_notifier_next - get the next drm_gpusvm_notifier in
> the list
> + * @notifier: a pointer to the current drm_gpusvm_notifier
> + *
> + * Return: A pointer to the next drm_gpusvm_notifier if available,
> or NULL if
> + * the current notifier is the last one or if the input
> notifier is
> + * NULL.
> + */
> +static struct drm_gpusvm_notifier *
> +__drm_gpusvm_notifier_next(struct drm_gpusvm_notifier *notifier)
> +{
> + if (notifier && !list_is_last(¬ifier->rb.entry,
> + ¬ifier->gpusvm-
> >notifier_list))
> + return list_next_entry(notifier, rb.entry);
Why aren't we using notifier_iter_next() here? Then the linked list
could be skipped.
> +
> + return NULL;
> +}
> +
> +/**
> + * drm_gpusvm_for_each_notifier - Iterate over GPU SVM notifiers in
> a gpusvm
> + * @notifier__: Iterator variable for the notifiers
> + * @notifier__: Pointer to the GPU SVM notifier
> + * @start__: Start address of the notifier
> + * @end__: End address of the notifier
> + *
> + * This macro is used to iterate over GPU SVM notifiers in a gpusvm.
> + */
> +#define drm_gpusvm_for_each_notifier(notifier__, gpusvm__, start__,
> end__) \
> + for ((notifier__) = notifier_iter_first(&(gpusvm__)->root,
> (start__), (end__) - 1); \
> + (notifier__) && (notifier__->interval.start <
> (end__)); \
> + (notifier__) = __drm_gpusvm_notifier_next(notifier__))
> +
Looks like end__ is not honored except for the first iteration. Relates
to the above question.
> +/**
> + * drm_gpusvm_for_each_notifier_safe - Safely iterate over GPU SVM
> notifiers in a gpusvm
> + * @notifier__: Iterator variable for the notifiers
> + * @next__: Iterator variable for the notifiers temporay storage
> + * @notifier__: Pointer to the GPU SVM notifier
> + * @start__: Start address of the notifier
> + * @end__: End address of the notifier
> + *
> + * This macro is used to iterate over GPU SVM notifiers in a gpusvm
> while
> + * removing notifiers from it.
> + */
> +#define drm_gpusvm_for_each_notifier_safe(notifier__, next__,
> gpusvm__, start__, end__) \
> + for ((notifier__) = notifier_iter_first(&(gpusvm__)->root,
> (start__), (end__) - 1), \
> + (next__) =
> __drm_gpusvm_notifier_next(notifier__); \
> + (notifier__) && (notifier__->interval.start <
> (end__)); \
> + (notifier__) = (next__), (next__) =
> __drm_gpusvm_notifier_next(notifier__))
Same here.
> +
> +/**
> + * drm_gpusvm_notifier_invalidate - Invalidate a GPU SVM notifier.
> + * @mni: Pointer to the mmu_interval_notifier structure.
> + * @mmu_range: Pointer to the mmu_notifier_range structure.
> + * @cur_seq: Current sequence number.
> + *
> + * This function serves as a generic MMU notifier for GPU SVM. It
> sets the MMU
> + * notifier sequence number and calls the driver invalidate vfunc
> under
> + * gpusvm->notifier_lock.
> + *
> + * Returns:
> + * true if the operation succeeds, false otherwise.
> + */
> +static bool
> +drm_gpusvm_notifier_invalidate(struct mmu_interval_notifier *mni,
> + const struct mmu_notifier_range
> *mmu_range,
> + unsigned long cur_seq)
> +{
> + struct drm_gpusvm_notifier *notifier =
> + container_of(mni, typeof(*notifier), notifier);
> + struct drm_gpusvm *gpusvm = notifier->gpusvm;
> +
> + if (!mmu_notifier_range_blockable(mmu_range))
> + return false;
> +
> + down_write(&gpusvm->notifier_lock);
> + mmu_interval_set_seq(mni, cur_seq);
> + gpusvm->ops->invalidate(gpusvm, notifier, mmu_range);
> + up_write(&gpusvm->notifier_lock);
> +
> + return true;
> +}
> +
> +/**
> + * drm_gpusvm_notifier_ops - MMU interval notifier operations for
> GPU SVM
> + */
> +static const struct mmu_interval_notifier_ops
> drm_gpusvm_notifier_ops = {
> + .invalidate = drm_gpusvm_notifier_invalidate,
> +};
> +
> +/**
> + * drm_gpusvm_init - Initialize the GPU SVM.
> + * @gpusvm: Pointer to the GPU SVM structure.
> + * @name: Name of the GPU SVM.
> + * @drm: Pointer to the DRM device structure.
> + * @mm: Pointer to the mm_struct for the address space.
> + * @device_private_page_owner: Device private pages owner.
> + * @mm_start: Start address of GPU SVM.
> + * @mm_range: Range of the GPU SVM.
> + * @notifier_size: Size of individual notifiers.
> + * @ops: Pointer to the operations structure for GPU SVM.
> + * @chunk_sizes: Pointer to the array of chunk sizes used in range
> allocation.
> + * Entries should be powers of 2 in descending order
> with last
> + * entry being SZ_4K.
> + * @num_chunks: Number of chunks.
> + *
> + * This function initializes the GPU SVM.
> + *
> + * Returns:
> + * 0 on success, a negative error code on failure.
> + */
> +int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
> + const char *name, struct drm_device *drm,
> + struct mm_struct *mm, void
> *device_private_page_owner,
> + u64 mm_start, u64 mm_range, u64 notifier_size,
> + const struct drm_gpusvm_ops *ops,
> + const u64 *chunk_sizes, int num_chunks)
> +{
> + if (!ops->invalidate || !num_chunks)
> + return -EINVAL;
> +
> + gpusvm->name = name;
> + gpusvm->drm = drm;
> + gpusvm->mm = mm;
> + gpusvm->device_private_page_owner =
> device_private_page_owner;
> + gpusvm->mm_start = mm_start;
> + gpusvm->mm_range = mm_range;
> + gpusvm->notifier_size = notifier_size;
> + gpusvm->ops = ops;
> + gpusvm->chunk_sizes = chunk_sizes;
> + gpusvm->num_chunks = num_chunks;
> +
> + mmgrab(mm);
> + gpusvm->root = RB_ROOT_CACHED;
> + INIT_LIST_HEAD(&gpusvm->notifier_list);
> +
> + init_rwsem(&gpusvm->notifier_lock);
> +
> + fs_reclaim_acquire(GFP_KERNEL);
> + might_lock(&gpusvm->notifier_lock);
> + fs_reclaim_release(GFP_KERNEL);
> +
> + return 0;
> +}
> +
> +/**
> + * drm_gpusvm_notifier_find - Find GPU SVM notifier
> + * @gpusvm__: Pointer to the GPU SVM structure
> + * @fault_addr__: Fault address
> + *
> + * This macro finds the GPU SVM notifier associated with the fault
> address.
> + *
> + * Returns:
> + * Pointer to the GPU SVM notifier on success, NULL otherwise.
> + */
> +#define drm_gpusvm_notifier_find(gpusvm__, fault_addr__) \
> + notifier_iter_first(&(gpusvm__)->root, (fault_addr__), \
> + (fault_addr__ + 1))
> +
> +/**
> + * to_drm_gpusvm_notifier - retrieve the container struct for a
> given rbtree node
> + * @node__: a pointer to the rbtree node embedded within a
> drm_gpusvm_notifier struct
> + *
> + * Return: A pointer to the containing drm_gpusvm_notifier
> structure.
> + */
> +#define to_drm_gpusvm_notifier(__node) \
> + container_of((__node), struct drm_gpusvm_notifier, rb.node)
> +
There appears to be a number of function-like macros in the code, which
look like they can be converted to functions. Linux prefers functions
over macros when possible:
https://www.kernel.org/doc/html/v5.8/process/coding-style.html#macros-enums-and-rtl
> +/**
> + * drm_gpusvm_notifier_insert - Insert GPU SVM notifier
> + * @gpusvm: Pointer to the GPU SVM structure
> + * @notifier: Pointer to the GPU SVM notifier structure
> + *
> + * This function inserts the GPU SVM notifier into the GPU SVM RB
> tree and list.
> + */
> +static void drm_gpusvm_notifier_insert(struct drm_gpusvm *gpusvm,
> + struct drm_gpusvm_notifier
> *notifier)
> +{
> + struct rb_node *node;
> + struct list_head *head;
> +
> + notifier_insert(notifier, &gpusvm->root);
> +
> + node = rb_prev(¬ifier->rb.node);
> + if (node)
> + head = &(to_drm_gpusvm_notifier(node))->rb.entry;
> + else
> + head = &gpusvm->notifier_list;
> +
> + list_add(¬ifier->rb.entry, head);
> +}
> +
> +/**
> + * drm_gpusvm_notifier_remove - Remove GPU SVM notifier
> + * @gpusvm__: Pointer to the GPU SVM tructure
> + * @notifier__: Pointer to the GPU SVM notifier structure
> + *
> + * This macro removes the GPU SVM notifier from the GPU SVM RB tree
> and list.
> + */
> +#define drm_gpusvm_notifier_remove(gpusvm__, notifier__) \
> + notifier_remove((notifier__), &(gpusvm__)->root); \
> + list_del(&(notifier__)->rb.entry)
Unless this can be made a function, Pls use
do { } while (0)
> +
> +/**
> + * drm_gpusvm_fini - Finalize the GPU SVM.
> + * @gpusvm: Pointer to the GPU SVM structure.
> + *
> + * This function finalizes the GPU SVM by cleaning up any remaining
> ranges and
> + * notifiers, and dropping a reference to struct MM.
> + */
> +void drm_gpusvm_fini(struct drm_gpusvm *gpusvm)
> +{
> + struct drm_gpusvm_notifier *notifier, *next;
> +
> + drm_gpusvm_for_each_notifier_safe(notifier, next, gpusvm, 0,
> LONG_MAX) {
> + struct drm_gpusvm_range *range, *__next;
> +
> + /*
> + * Remove notifier first to avoid racing with any
> invalidation
> + */
> + mmu_interval_notifier_remove(¬ifier->notifier);
> + notifier->flags.removed = true;
> +
> + drm_gpusvm_for_each_range_safe(range, __next,
> notifier, 0,
> + LONG_MAX)
> + drm_gpusvm_range_remove(gpusvm, range);
> + }
> +
> + mmdrop(gpusvm->mm);
> + WARN_ON(!RB_EMPTY_ROOT(&gpusvm->root.rb_root));
> +}
> +
> +/**
> + * drm_gpusvm_notifier_alloc - Allocate GPU SVM notifier
> + * @gpusvm: Pointer to the GPU SVM structure
> + * @fault_addr: Fault address
> + *
> + * This function allocates and initializes the GPU SVM notifier
> structure.
> + *
> + * Returns:
> + * Pointer to the allocated GPU SVM notifier on success, ERR_PTR()
> on failure.
> + */
> +static struct drm_gpusvm_notifier *
> +drm_gpusvm_notifier_alloc(struct drm_gpusvm *gpusvm, u64 fault_addr)
> +{
> + struct drm_gpusvm_notifier *notifier;
> +
> + if (gpusvm->ops->notifier_alloc)
> + notifier = gpusvm->ops->notifier_alloc();
> + else
> + notifier = kzalloc(sizeof(*notifier), GFP_KERNEL);
> +
> + if (!notifier)
> + return ERR_PTR(-ENOMEM);
> +
> + notifier->gpusvm = gpusvm;
> + notifier->interval.start = ALIGN_DOWN(fault_addr, gpusvm-
> >notifier_size);
> + notifier->interval.end = ALIGN(fault_addr + 1, gpusvm-
> >notifier_size);
> + INIT_LIST_HEAD(¬ifier->rb.entry);
> + notifier->root = RB_ROOT_CACHED;
> + INIT_LIST_HEAD(¬ifier->range_list);
> +
> + return notifier;
> +}
> +
> +/**
> + * drm_gpusvm_notifier_free - Free GPU SVM notifier
> + * @gpusvm: Pointer to the GPU SVM structure
> + * @notifier: Pointer to the GPU SVM notifier structure
> + *
> + * This function frees the GPU SVM notifier structure.
> + */
> +static void drm_gpusvm_notifier_free(struct drm_gpusvm *gpusvm,
> + struct drm_gpusvm_notifier
> *notifier)
> +{
> + WARN_ON(!RB_EMPTY_ROOT(¬ifier->root.rb_root));
> +
> + if (gpusvm->ops->notifier_free)
> + gpusvm->ops->notifier_free(notifier);
> + else
> + kfree(notifier);
> +}
> +
> +/**
> + * to_drm_gpusvm_range - retrieve the container struct for a given
> rbtree node
> + * @node__: a pointer to the rbtree node embedded within a
> drm_gpusvm_range struct
> + *
> + * Return: A pointer to the containing drm_gpusvm_range structure.
> + */
> +#define to_drm_gpusvm_range(node__) \
> + container_of((node__), struct drm_gpusvm_range, rb.node)
> +
> +/**
> + * drm_gpusvm_range_insert - Insert GPU SVM range
> + * @notifier: Pointer to the GPU SVM notifier structure
> + * @range: Pointer to the GPU SVM range structure
> + *
> + * This function inserts the GPU SVM range into the notifier RB tree
> and list.
> + */
> +static void drm_gpusvm_range_insert(struct drm_gpusvm_notifier
> *notifier,
> + struct drm_gpusvm_range *range)
> +{
> + struct rb_node *node;
> + struct list_head *head;
> +
> + drm_gpusvm_notifier_lock(notifier->gpusvm);
> + range_insert(range, ¬ifier->root);
> +
> + node = rb_prev(&range->rb.node);
> + if (node)
> + head = &(to_drm_gpusvm_range(node))->rb.entry;
> + else
> + head = ¬ifier->range_list;
> +
> + list_add(&range->rb.entry, head);
> + drm_gpusvm_notifier_unlock(notifier->gpusvm);
> +}
> +
> +/**
> + * __drm_gpusvm_range_remove - Remove GPU SVM range
> + * @notifier__: Pointer to the GPU SVM notifier structure
> + * @range__: Pointer to the GPU SVM range structure
> + *
> + * This macro removes the GPU SVM range from the notifier RB tree
> and list.
> + */
> +#define __drm_gpusvm_range_remove(notifier__, range__) \
> + range_remove((range__), &(notifier__)->root); \
> + list_del(&(range__)->rb.entry)
Same thing as for the notifier rb tree. And do we need the linked list?
> +
> +/**
> + * 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,
> + u64 fault_addr, u64 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->va.start = ALIGN_DOWN(fault_addr, chunk_size);
> + range->va.end = ALIGN(fault_addr + 1, chunk_size);
> + INIT_LIST_HEAD(&range->rb.entry);
> + range->notifier_seq = LONG_MAX;
> + range->flags.migrate_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,
> + u64 start, u64 end)
> +{
> + struct hmm_range hmm_range = {
> + .default_flags = 0,
> + .notifier = ¬ifier->notifier,
> + .start = start,
> + .end = end,
> + .dev_private_owner = gpusvm-
> >device_private_page_owner,
> + };
> + unsigned long timeout =
> + jiffies +
> msecs_to_jiffies(HMM_RANGE_DEFAULT_TIMEOUT);
> + unsigned long *pfns;
> + unsigned long npages = npages_in_range(start, end);
> + int err, i;
> +
> + mmap_assert_locked(gpusvm->mm);
> +
> + pfns = kvmalloc_array(npages, sizeof(*pfns), GFP_KERNEL);
> + if (!pfns)
> + return false;
> +
> + hmm_range.notifier_seq = mmu_interval_read_begin(¬ifier-
> >notifier);
> + hmm_range.hmm_pfns = pfns;
> +
> + while (true) {
> + err = hmm_range_fault(&hmm_range);
> + if (err == -EBUSY) {
> + if (time_after(jiffies, timeout))
> + break;
> +
> + hmm_range.notifier_seq =
> mmu_interval_read_begin(¬ifier->notifier);
> + continue;
> + }
> + break;
> + }
> + if (err)
> + goto err_free;
> +
> + for (i = 0; i < npages;) {
> + 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
> + * @fault_addr: Fault address
> + * @gpuva_start: Start address of GPUVA which mirrors CPU
> + * @gpuva_end: End address of GPUVA which mirrors CPU
> + * @check_pages: Flag indicating whether to check pages
> + *
> + * This function determines the chunk size for the GPU SVM range
> based on the
> + * fault address, GPU SVM chunk sizes, existing GPU SVM ranges, and
> the virtual
> + * memory area boundaries.
> + *
> + * Returns:
> + * Chunk size on success, LONG_MAX on failure.
> + */
> +static u64 drm_gpusvm_range_chunk_size(struct drm_gpusvm *gpusvm,
> + struct drm_gpusvm_notifier
> *notifier,
> + struct vm_area_struct *vas,
> + u64 fault_addr, u64
> gpuva_start,
> + u64 gpuva_end, bool
> check_pages)
> +{
> + u64 start, end;
> + int i = 0;
> +
> +retry:
> + for (; i < gpusvm->num_chunks; ++i) {
> + start = ALIGN_DOWN(fault_addr, gpusvm-
> >chunk_sizes[i]);
> + end = ALIGN(fault_addr + 1, gpusvm->chunk_sizes[i]);
> +
> + if (start >= vas->vm_start && end <= vas->vm_end &&
> + start >= notifier->interval.start &&
> + end <= notifier->interval.end &&
> + start >= gpuva_start && end <= gpuva_end)
> + break;
> + }
> +
> + if (i == gpusvm->num_chunks)
> + return LONG_MAX;
> +
> + /*
> + * If allocation more than page, ensure not to overlap with
> existing
> + * ranges.
> + */
> + if (end - start != SZ_4K) {
> + struct drm_gpusvm_range *range;
> +
> + range = drm_gpusvm_range_find(notifier, start, end);
> + if (range) {
> + ++i;
> + goto retry;
> + }
> +
> + /*
> + * XXX: Only create range on pages CPU has faulted
> in. Without
> + * this check, or prefault, on BMG
> 'xe_exec_system_allocator --r
> + * process-many-malloc' fails. In the failure case,
> each process
> + * mallocs 16k but the CPU VMA is ~128k which
> results in 64k SVM
> + * ranges. When migrating the SVM ranges, some
> processes fail in
> + * drm_gpusvm_migrate_to_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.
> + */
Needs to be figured out. I think even in the system allocator case, if
a user uses malloc() to allocate a GPU only buffer we'd need to support
that?
> + if (check_pages &&
> + !drm_gpusvm_check_pages(gpusvm, notifier, start,
> end)) {
> + ++i;
> + goto retry;
> + }
> + }
> +
> + return end - start;
> +}
> +
> +/**
> + * drm_gpusvm_range_find_or_insert - Find or insert GPU SVM range
> + * @gpusvm: Pointer to the GPU SVM structure
> + * @fault_addr: Fault address
> + * @gpuva_start: Start address of GPUVA which mirrors CPU
> + * @gpuva_end: End address of GPUVA which mirrors CPU
> + * @ctx: GPU SVM context
> + *
> + * This function finds or inserts a newly allocated a GPU SVM range
> based on the
> + * fault address. Caller must hold a lock to protect range lookup
> and insertion.
> + *
> + * Returns:
> + * Pointer to the GPU SVM range on success, ERR_PTR() on failure.
> + */
> +struct drm_gpusvm_range *
> +drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm, u64
> fault_addr,
> + u64 gpuva_start, u64 gpuva_end,
> + const struct drm_gpusvm_ctx *ctx)
> +{
> + struct drm_gpusvm_notifier *notifier;
> + struct drm_gpusvm_range *range;
> + struct mm_struct *mm = gpusvm->mm;
> + struct vm_area_struct *vas;
> + bool notifier_alloc = false;
> + u64 chunk_size;
> + int err;
> + bool migrate_devmem;
> +
> + if (fault_addr < gpusvm->mm_start ||
> + fault_addr > gpusvm->mm_start + gpusvm->mm_range) {
return ERR_PTR(-EINVAL)?
> + err = -EINVAL;
> + goto err_out;
> + }
> +
> + if (!mmget_not_zero(mm)) {
> + err = -EFAULT;
> + goto err_out;
> + }
> +
> + 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-
> >interval.start,
> + notifier-
> >interval.end -
> + notifier-
> >interval.start,
> +
> &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);
> + 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);
> +err_out:
> + return ERR_PTR(err);
> +}
> +
> +/**
> + * __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 free pages associated with a GPU SVM range.
Frees the dma address array
> + */
> +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->va.start,
> range->va.end);
> + struct drm_gpusvm_notifier *notifier;
> +
> + notifier = drm_gpusvm_notifier_find(gpusvm, range-
> >va.start);
> + if (WARN_ON_ONCE(!notifier))
> + return;
> +
> + drm_gpusvm_notifier_lock(gpusvm);
> + __drm_gpusvm_range_unmap_pages(gpusvm, range, 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);
> + }
> +}
> +
> +/**
> + * drm_gpusvm_range_get - Get a reference to GPU SVM range
> + * @range: Pointer to the GPU SVM range
> + *
> + * This function increments the reference count of the specified GPU
> SVM range.
> + *
> + * Returns:
> + * Pointer to the GPU SVM range.
> + */
> +struct drm_gpusvm_range *
> +drm_gpusvm_range_get(struct drm_gpusvm_range *range)
> +{
> + kref_get(&range->refcount);
> +
> + return range;
> +}
> +
> +/**
> + * drm_gpusvm_range_destroy - Destroy GPU SVM range
> + * @refcount: Pointer to the reference counter embedded in the GPU
> SVM range
> + *
> + * This function destroys the specified GPU SVM range when its
> reference count
> + * reaches zero. If a custom range-free function is provided, it is
> invoked to
> + * free the range; otherwise, the range is deallocated using
> kfree().
> + */
> +static void drm_gpusvm_range_destroy(struct kref *refcount)
> +{
> + struct drm_gpusvm_range *range =
> + container_of(refcount, struct drm_gpusvm_range,
> refcount);
> + struct drm_gpusvm *gpusvm = range->gpusvm;
> +
> + if (gpusvm->ops->range_free)
> + gpusvm->ops->range_free(range);
> + else
> + kfree(range);
> +}
> +
> +/**
> + * drm_gpusvm_range_put - Put a reference to GPU SVM range
> + * @range: Pointer to the GPU SVM range
> + *
> + * This function decrements the reference count of the specified GPU
> SVM range
> + * and frees it when the count reaches zero.
> + */
> +void drm_gpusvm_range_put(struct drm_gpusvm_range *range)
> +{
> + kref_put(&range->refcount, drm_gpusvm_range_destroy);
> +}
> +
> +/**
> + * drm_gpusvm_range_pages_valid - GPU SVM range pages valid
> + * @gpusvm: Pointer to the GPU SVM structure
> + * @range: Pointer to the GPU SVM range structure
> + *
> + * This function determines if a GPU SVM range pages are valid.
> Expected be
> + * called holding gpusvm->notifier_lock and as the last step before
> commiting a
> + * GPU binding.
> + *
> + * Returns:
> + * True if GPU SVM range has valid pages, False otherwise
> + */
> +bool drm_gpusvm_range_pages_valid(struct drm_gpusvm *gpusvm,
> + struct drm_gpusvm_range *range)
> +{
> + lockdep_assert_held(&gpusvm->notifier_lock);
> +
> + return range->flags.has_devmem_pages || range-
> >flags.has_dma_mapping;
> +}
> +
> +/**
> + * drm_gpusvm_range_pages_valid_unlocked - GPU SVM range pages valid
> unlocked
> + * @gpusvm: Pointer to the GPU SVM structure
> + * @range: Pointer to the GPU SVM range structure
> + *
> + * This function determines if a GPU SVM range pages are valid.
> Expected be
> + * called without holding gpusvm->notifier_lock.
> + *
> + * Returns:
> + * True if GPU SVM range has valid pages, False otherwise
> + */
> +static bool
> +drm_gpusvm_range_pages_valid_unlocked(struct drm_gpusvm *gpusvm,
> + struct drm_gpusvm_range
> *range)
> +{
> + bool pages_valid;
> +
> + if (!range->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->va.start,
> + .end = range->va.end,
> + .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->va.start,
> range->va.end);
> + 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_out;
> + }
> +
> + 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);
> + 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;
I suppose before merging we want to support mixed ranges since
migration is best effort only, or what are the plans here?
> + 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);
> +err_out:
> + if (err == -EAGAIN)
> + goto retry;
> + return err;
> +}
> +
> +/**
> + * drm_gpusvm_range_unmap_pages - Unmap pages associated with a GPU
> SVM range
> + * @gpusvm: Pointer to the GPU SVM structure
> + * @range: Pointer to the GPU SVM range structure
> + * @ctx: GPU SVM context
> + *
> + * This function unmaps pages associated with a GPU SVM range. If
> @in_notifier
> + * is set, it is assumed that gpusvm->notifier_lock is held in write
> mode; if it
> + * is clear, it acquires gpusvm->notifier_lock in read mode. Must be
> called on
> + * each GPU SVM range attached to notifier in gpusvm->ops-
> >invalidate for IOMMU
> + * security model.
> + */
> +void drm_gpusvm_range_unmap_pages(struct drm_gpusvm *gpusvm,
> + struct drm_gpusvm_range *range,
> + const struct drm_gpusvm_ctx *ctx)
> +{
> + unsigned long npages = npages_in_range(range->va.start,
> range->va.end);
> +
> + 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);
> +}
NIT: Separate functions for locked / unlocked makes life easier for
static code analyzers.
Section below I think should belong to drm_pagemap.c
> +
> +/**
> + * drm_gpusvm_migration_put_page - Put a migration page
> + * @page: Pointer to the page to put
> + *
> + * This function unlocks and puts a page.
> + */
> +static void drm_gpusvm_migration_put_page(struct page *page)
_unlock_put_page()?
> +{
> + unlock_page(page);
> + put_page(page);
> +}
> +
> +/**
> + * drm_gpusvm_migration_put_pages - Put migration pages
> + * @npages: Number of pages
> + * @migrate_pfn: Array of migrate page frame numbers
> + *
> + * This function puts an array of pages.
> + */
> +static void drm_gpusvm_migration_put_pages(unsigned long npages,
> + unsigned long
> *migrate_pfn)
> +{
> + unsigned long i;
> +
> + for (i = 0; i < npages; ++i) {
> + if (!migrate_pfn[i])
> + continue;
> +
> + drm_gpusvm_migration_put_page(migrate_pfn_to_page(mi
> grate_pfn[i]));
> + migrate_pfn[i] = 0;
> + }
> +}
> +
> +/**
> + * drm_gpusvm_get_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,
> + long unsigned int
> *migrate_pfn,
> + unsigned long npages,
> + enum dma_data_direction dir)
> +{
> + unsigned long i;
> +
> + for (i = 0; i < npages; ++i) {
> + struct page *page =
> migrate_pfn_to_page(migrate_pfn[i]);
> +
> + if (!page)
> + continue;
> +
> + if (WARN_ON_ONCE(is_zone_device_page(page)))
> + return -EFAULT;
> +
> + dma_addr[i] = dma_map_page(dev, page, 0, PAGE_SIZE,
> dir);
> + if (dma_mapping_error(dev, dma_addr[i]))
> + return -EFAULT;
> + }
> +
> + return 0;
> +}
TBC'd
/Thomas
