On Thu, Jun 18, 2026 at 04:09:01PM +0800, Honglei Huang wrote:
> From: Honglei Huang <[email protected]>
>
> Since the pages the physical pages and MM VA range has been abstractly
> separated. Unbinding a single form of physical page from the MM VA
> range, brings flexibility to the drm gpu SVM framework, transfer the
> way of management of MM and device physical pages to the driver layer.
>
> framework's range embedded pages object and its range level wrappers
> have no users left. Remove the following:
>
> - Drop pages in drm_gpusvm_range.
> - Drop drm_gpusvm_range_pages_valid(), drm_gpusvm_range_get_pages()
> and drm_gpusvm_range_unmap_pages(); drivers should use the
> drm_gpusvm_pages helpers (drm_gpusvm_pages_valid,
> drm_gpusvm_get_pages, drm_gpusvm_unmap_pages) directly on a
> pages object they own.
> - Drop the notifier_seq seeding in drm_gpusvm_range_alloc();
> drivers initialise notifier_seq on their own pages object.
>
> Update the DOC: overview to match the new model: document struct
> drm_gpusvm_pages and the driver owned 1:1 / N:1 layouts, and rewrite the
> usage examples to operate on a driver embedded pages object by the
> drm_gpusvm_pages helpers instead of the removed range level wrappers.
>
> Suggested-by: Matthew Brost <[email protected]>
> Signed-off-by: Honglei Huang <[email protected]>
> ---
> drivers/gpu/drm/drm_gpusvm.c | 163 ++++++++++++++++++-----------------
> include/drm/drm_gpusvm.h | 13 ---
> 2 files changed, 84 insertions(+), 92 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
> index 85fbadc9716..842bfb37a36 100644
> --- a/drivers/gpu/drm/drm_gpusvm.c
> +++ b/drivers/gpu/drm/drm_gpusvm.c
> @@ -48,6 +48,47 @@
> * event. As mentioned above, ranges are tracked in a notifier's Red-Black
> * tree.
> *
> + * - Pages:
> + * struct drm_gpusvm_pages holds the DMA mapping state for a range of
> + * CPU virtual addresses: the DMA mapped device addresses,
> + * the device private pagemap, the IOVA state, the per mapping
> + * notifier sequence number, and the drm_device that owns the DMA
> + * mappings.
> + * A driver embeds one or more struct drm_gpusvm_pages alongside its
> + * struct drm_gpusvm_range, choosing one of two layouts:
> + *
> + * 1:1 - one drm_gpusvm_pages per range (one drm_device). Simplest
> + * layout; to mirror a VA range on several devices a driver uses a
> + * separate range (and notifier) per device, so the HMM fault is taken
> + * once per device.
> + *
> + * N:1 - one drm_gpusvm_pages per drm_device, all sharing one range and
> + * notifier; only the per-device DMA mapping differs. The instances must
> + * sit in contiguous memory so a single drm_gpusvm_range_set_unmapped()
> + * can mark them all. A driver can keep one instance inline for the single
> + * device case and switch to a heap array only when more devices join,
> + * e.g.:
> + *
> + * .. code-block:: c
> + *
> + * struct driver_range {
> + * struct drm_gpusvm_range base;
> + * unsigned int num_pages; // 1: inline_pages, >1: pages[]
> + * union {
> + * struct drm_gpusvm_pages inline_pages;
> + * struct drm_gpusvm_pages *pages;
> + * };
> + * };
> + *
> + * In the N:1 case the driver allocates the pages array (e.g. with
> + * kmalloc_array(num_pages, ...)), initialises each entry with
Sashiko suggests kcalloc here or drm_gpusvm_init_pages() zeros all fields.
I tend to lean towards alloc dynamic structs as zero and have init
functions set fields but either works for me. But the doc and
implementation should be consistent.
Matt
> + * drm_gpusvm_init_pages(), and frees each entry with
> + * drm_gpusvm_free_pages() plus the array itself, from its range free
> + * callback. Each drm_gpusvm_pages is mapped independently by their own
> + * drm_device.
> + * Each drm_gpusvm_pages must be initialised with drm_gpusvm_init_pages()
> + * and released with drm_gpusvm_free_pages() in driver range free callback.
> + *
> * - Operations:
> * Define the interface for driver-specific GPU SVM operations such as
> * range allocation, notifier allocation, and invalidations.
> @@ -92,7 +133,7 @@
> * 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.
> + * (drm_gpusvm_pages_valid) when the driver is committing GPU bindings.
> * This lock corresponds to the ``driver->update`` lock mentioned in
> * Documentation/mm/hmm.rst. Future revisions may transition from a GPU SVM
> * global lock to a per-notifier lock if finer-grained locking is deemed
> @@ -140,15 +181,20 @@
> *
> * .. code-block:: c
> *
> - * int driver_bind_range(struct drm_gpusvm *gpusvm, struct
> drm_gpusvm_range *range)
> + * struct driver_range {
> + * struct drm_gpusvm_range base;
> + * struct drm_gpusvm_pages pages;
> + * };
> + *
> + * int driver_bind_range(struct drm_gpusvm *gpusvm, struct driver_range
> *drange)
> * {
> * int err = 0;
> *
> - * driver_alloc_and_setup_memory_for_bind(gpusvm, range);
> + * driver_alloc_and_setup_memory_for_bind(gpusvm, drange);
> *
> * drm_gpusvm_notifier_lock(gpusvm);
> - * if (drm_gpusvm_range_pages_valid(range))
> - * driver_commit_bind(gpusvm, range);
> + * if (drm_gpusvm_pages_valid(gpusvm, &drange->pages))
> + * driver_commit_bind(gpusvm, drange);
> * else
> * err = -EAGAIN;
> * drm_gpusvm_notifier_unlock(gpusvm);
> @@ -160,6 +206,8 @@
> * unsigned long gpuva_start, unsigned long gpuva_end)
> * {
> * struct drm_gpusvm_ctx ctx = {};
> + * struct driver_range *drange;
> + * struct drm_gpusvm_range *range;
> * int err;
> *
> * driver_svm_lock();
> @@ -174,6 +222,7 @@
> * err = PTR_ERR(range);
> * goto unlock;
> * }
> + * drange = container_of(range, struct driver_range, base);
> *
> * if (driver_migration_policy(range)) {
> * err =
> drm_pagemap_populate_mm(driver_choose_drm_pagemap(),
> @@ -183,7 +232,10 @@
> * goto retry;
> * }
> *
> - * err = drm_gpusvm_range_get_pages(gpusvm, range, &ctx);
> + * err = drm_gpusvm_get_pages(gpusvm, &drange->pages,
> + * gpusvm->mm,
> &range->notifier->notifier,
> + * drm_gpusvm_range_start(range),
> + * drm_gpusvm_range_end(range), &ctx);
> * if (err == -EOPNOTSUPP || err == -EFAULT || err == -EPERM) {
> // CPU mappings changed
> * if (err == -EOPNOTSUPP)
> * drm_gpusvm_range_evict(gpusvm, range);
> @@ -192,7 +244,7 @@
> * goto unlock;
> * }
> *
> - * err = driver_bind_range(gpusvm, range);
> + * err = driver_bind_range(gpusvm, drange);
> * if (err == -EAGAIN) // CPU mappings changed
> * goto retry
> *
> @@ -205,6 +257,22 @@
> *
> * .. code-block:: c
> *
> + * // The driver owns the drm_gpusvm_pages lifecycle. The natural place
> + * // to release it is the ops->range_free callback, which the framework
> + * // invokes when the range refcount drops to zero inside
> + * // drm_gpusvm_range_remove(). drm_gpusvm_free_pages() unmaps any
> + * // lingering DMA mapping and a no-op if already unmapped and frees the
> + * // dma_addr array.
> + * void driver_range_free(struct drm_gpusvm_range *range)
> + * {
> + * struct driver_range *drange =
> + * container_of(range, struct driver_range, base);
> + *
> + * drm_gpusvm_free_pages(range->gpusvm, &drange->pages,
> + * drm_gpusvm_range_size(range) >>
> PAGE_SHIFT);
> + * kfree(drange);
> + * }
> + *
> * void __driver_garbage_collector(struct drm_gpusvm *gpusvm,
> * struct drm_gpusvm_range *range)
> * {
> @@ -215,6 +283,7 @@
> * drm_gpusvm_range_evict(gpusvm, range);
> *
> * driver_unbind_range(range);
> + * // Pages are released by driver_range_free() (ops->range_free).
> * drm_gpusvm_range_remove(gpusvm, range);
> * }
> *
> @@ -236,17 +305,22 @@
> * {
> * struct drm_gpusvm_ctx ctx = { .in_notifier = true, };
> * struct drm_gpusvm_range *range = NULL;
> + * struct driver_range *drange;
> *
> * 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);
> + * drange = container_of(range, struct driver_range, base);
> + *
> + * drm_gpusvm_unmap_pages(gpusvm, &drange->pages,
> + * drm_gpusvm_range_size(range) >>
> PAGE_SHIFT,
> + * &ctx);
> *
> * if (mmu_range->event != MMU_NOTIFY_UNMAP)
> * continue;
> *
> - * drm_gpusvm_range_set_unmapped(range, mmu_range);
> + * drm_gpusvm_range_set_unmapped(range, &drange->pages, 1,
> mmu_range);
> * driver_garbage_collector_add(gpusvm, range);
> * }
> * }
> @@ -640,8 +714,6 @@ drm_gpusvm_range_alloc(struct drm_gpusvm *gpusvm,
> 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->pages.notifier_seq = LONG_MAX;
> - range->pages.drm = gpusvm->drm;
> range->flags.migrate_devmem = migrate_devmem ? 1 : 0;
>
> return range;
> @@ -930,7 +1002,7 @@ drm_gpusvm_range_chunk_size(struct drm_gpusvm *gpusvm,
> * mallocs 16k but the CPU VMA is ~128k which results in 64k SVM
> * ranges. When migrating the SVM ranges, some processes fail in
> * drm_pagemap_migrate_to_devmem with 'migrate.cpages != npages'
> - * and then upon drm_gpusvm_range_get_pages device pages from
> + * and then upon drm_gpusvm_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
> @@ -1335,27 +1407,6 @@ bool drm_gpusvm_pages_valid(struct drm_gpusvm *gpusvm,
> }
> EXPORT_SYMBOL_GPL(drm_gpusvm_pages_valid);
>
> -/**
> - * 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.
> - *
> - * Return: 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)
> -{
> - return drm_gpusvm_pages_valid(gpusvm, &range->pages);
> -}
> -EXPORT_SYMBOL_GPL(drm_gpusvm_range_pages_valid);
> -
> /**
> * drm_gpusvm_pages_valid_unlocked() - GPU SVM pages valid unlocked
> * @gpusvm: Pointer to the GPU SVM structure
> @@ -1636,29 +1687,6 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
> }
> EXPORT_SYMBOL_GPL(drm_gpusvm_get_pages);
>
> -/**
> - * 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.
> - *
> - * Return: 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)
> -{
> - return drm_gpusvm_get_pages(gpusvm, &range->pages,
> - gpusvm->mm,
> - &range->notifier->notifier,
> - drm_gpusvm_range_start(range),
> - drm_gpusvm_range_end(range), ctx);
> -}
> -EXPORT_SYMBOL_GPL(drm_gpusvm_range_get_pages);
> -
> /**
> * drm_gpusvm_unmap_pages() - Unmap GPU svm pages
> * @gpusvm: Pointer to the GPU SVM structure
> @@ -1689,29 +1717,6 @@ void drm_gpusvm_unmap_pages(struct drm_gpusvm *gpusvm,
> }
> EXPORT_SYMBOL_GPL(drm_gpusvm_unmap_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(drm_gpusvm_range_start(range),
> - drm_gpusvm_range_end(range));
> -
> - return drm_gpusvm_unmap_pages(gpusvm, &range->pages, npages, ctx);
> -}
> -EXPORT_SYMBOL_GPL(drm_gpusvm_range_unmap_pages);
> -
> /**
> * drm_gpusvm_range_evict() - Evict GPU SVM range
> * @gpusvm: Pointer to the GPU SVM structure
> diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h
> index e32d3bcb47b..5edfa7d0c36 100644
> --- a/include/drm/drm_gpusvm.h
> +++ b/include/drm/drm_gpusvm.h
> @@ -177,7 +177,6 @@ struct drm_gpusvm_range_flags {
> * @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
> - * @pages: The pages for this range.
> * @flags: Flags for range see &struct drm_gpusvm_range_flags
> *
> * This structure represents a GPU SVM range used for tracking memory ranges
> @@ -189,7 +188,6 @@ struct drm_gpusvm_range {
> struct kref refcount;
> struct interval_tree_node itree;
> struct list_head entry;
> - struct drm_gpusvm_pages pages;
> struct drm_gpusvm_range_flags flags;
> };
>
> @@ -307,20 +305,9 @@ 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);
> -
> bool drm_gpusvm_pages_valid(struct drm_gpusvm *gpusvm,
> struct drm_gpusvm_pages *svm_pages);
>
> -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);
> -
> bool drm_gpusvm_has_mapping(struct drm_gpusvm *gpusvm, unsigned long start,
> unsigned long end);
>
> --
> 2.34.1
>
