On Thu, Apr 30, 2026 at 12:36:41PM -0700, Matthew Brost wrote:On Thu, Apr 30, 2026 at 03:41:30PM +0530, Arvind Yadav wrote:xe_bo_recompute_purgeable_state() walks all VMAs of a BO to determine whether the BO can be made purgeable. This makes VMA create/destroy and madvise updates O(n) in the number of mappings. Replace the walk with BO-local counters protected by the BO dma-resv lock: - vma_count tracks the number of VMAs mapping the BO. - willneed_count tracks active WILLNEED holders, including WILLNEED VMAs and active dma-buf exports for non-imported BOs. A DONTNEED BO is promoted back to WILLNEED on a 0->1 transition of willneed_count. A BO is demoted to DONTNEED on a 1->0 transition only when it still has VMAs, preserving the previous behaviour where a BO with no mappings keeps its current madvise state. PURGED remains terminal, preserving the existing "once purged, always purged" rule. v2: - Use early return for imported BOs in all four helpers to avoid nesting (Matt B). - Group purgeability state into a purgeable sub-struct on struct xe_bo (Matt B). - Reword xe_bo_willneed_put_locked() kernel-doc to explain that a 1->0 transition means all remaining active VMAs are DONTNEED (Matt B). Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Matthew Brost <matthew.brost@intel.com>Reviewed-by: Matthew Brost <matthew.brost@intel.com>My bad - sashiko flagged a valid issue here [1]. So I xe_vma_create need to flags.check_purged check that is currently in vma_lock_and_validate(). We the dma-resv locks in xe_vma_create so moving the check to xe_vma_create should be safe. More below. [1] https://sashiko.dev/#/patchset/20260430101130.1365878-1-arvind.yadav%40intel.com
Yes, Good catch. we should add the check in xe_vma_create(), but it also needs to remain in vma_lock_and_validate() because PREFETCH does not go through xe_vma_create(). drm_gpuvm_prefetch_ops_create() generates operations that reference existing VMAs, and the PREFETCH path in op_lock_and_prep() relies solely on vma_lock_and_validate().
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com> Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com> Signed-off-by: Arvind Yadav <arvind.yadav@intel.com> --- drivers/gpu/drm/xe/xe_bo.c | 6 +- drivers/gpu/drm/xe/xe_bo.h | 88 +++++++++++++++- drivers/gpu/drm/xe/xe_bo_types.h | 27 ++++- drivers/gpu/drm/xe/xe_dma_buf.c | 28 ++++- drivers/gpu/drm/xe/xe_vm.c | 9 +- drivers/gpu/drm/xe/xe_vm_madvise.c | 162 ++--------------------------- drivers/gpu/drm/xe/xe_vm_madvise.h | 2 - 7 files changed, 155 insertions(+), 167 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c index 5ce60d161e09..eaa3a4ee9111 100644 --- a/drivers/gpu/drm/xe/xe_bo.c +++ b/drivers/gpu/drm/xe/xe_bo.c @@ -884,10 +884,10 @@ void xe_bo_set_purgeable_state(struct xe_bo *bo, new_state == XE_MADV_PURGEABLE_PURGED); /* Once purged, always purged - cannot transition out */ - xe_assert(xe, !(bo->madv_purgeable == XE_MADV_PURGEABLE_PURGED && + xe_assert(xe, !(bo->purgeable.state == XE_MADV_PURGEABLE_PURGED && new_state != XE_MADV_PURGEABLE_PURGED)); - bo->madv_purgeable = new_state; + bo->purgeable.state = new_state; xe_bo_set_purgeable_shrinker(bo, new_state); } @@ -2355,7 +2355,7 @@ struct xe_bo *xe_bo_init_locked(struct xe_device *xe, struct xe_bo *bo, INIT_LIST_HEAD(&bo->vram_userfault_link); /* Initialize purge advisory state */ - bo->madv_purgeable = XE_MADV_PURGEABLE_WILLNEED; + bo->purgeable.state = XE_MADV_PURGEABLE_WILLNEED; drm_gem_private_object_init(&xe->drm, &bo->ttm.base, size); diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h index 68dea7d25a6b..6340317f7d2e 100644 --- a/drivers/gpu/drm/xe/xe_bo.h +++ b/drivers/gpu/drm/xe/xe_bo.h @@ -251,7 +251,7 @@ static inline bool xe_bo_is_protected(const struct xe_bo *bo) static inline bool xe_bo_is_purged(struct xe_bo *bo) { xe_bo_assert_held(bo); - return bo->madv_purgeable == XE_MADV_PURGEABLE_PURGED; + return bo->purgeable.state == XE_MADV_PURGEABLE_PURGED; } /** @@ -268,11 +268,95 @@ static inline bool xe_bo_is_purged(struct xe_bo *bo) static inline bool xe_bo_madv_is_dontneed(struct xe_bo *bo) { xe_bo_assert_held(bo); - return bo->madv_purgeable == XE_MADV_PURGEABLE_DONTNEED; + return bo->purgeable.state == XE_MADV_PURGEABLE_DONTNEED; } void xe_bo_set_purgeable_state(struct xe_bo *bo, enum xe_madv_purgeable_state new_state); +/** + * xe_bo_willneed_get_locked() - Acquire a WILLNEED holder on a BO + * @bo: Buffer object + * + * Increments willneed_count and, on a 0->1 transition, promotes the BO + * from DONTNEED to WILLNEED. PURGED is terminal and is never modified. + * + * Caller must hold the BO's dma-resv lock. + */ +static inline void xe_bo_willneed_get_locked(struct xe_bo *bo) +{ + xe_bo_assert_held(bo); + + /* Imported BOs are owned externally; do not track purgeability. */ + if (drm_gem_is_imported(&bo->ttm.base)) + return; + + if (bo->purgeable.willneed_count++ == 0 && xe_bo_madv_is_dontneed(bo)) + xe_bo_set_purgeable_state(bo, XE_MADV_PURGEABLE_WILLNEED); +} + +/** + * xe_bo_willneed_put_locked() - Release a WILLNEED holder on a BO + * @bo: Buffer object + * + * Decrements willneed_count and, on a 1->0 transition, marks the BO + * DONTNEED only if it still has VMAs (implying all active VMAs are + * DONTNEED). If the last VMA is being removed, preserve the current BO + * state to match the previous VMA-walk semantics. + * + * PURGED is terminal and the BO state is never modified. + * + * Caller must hold the BO's dma-resv lock. + */ +static inline void xe_bo_willneed_put_locked(struct xe_bo *bo) +{ + xe_bo_assert_held(bo); + + if (drm_gem_is_imported(&bo->ttm.base)) + return; + + xe_assert(xe_bo_device(bo), bo->purgeable.willneed_count > 0); + if (--bo->purgeable.willneed_count == 0 && bo->purgeable.vma_count > 0 && + !xe_bo_is_purged(bo)) + xe_bo_set_purgeable_state(bo, XE_MADV_PURGEABLE_DONTNEED); +} + +/** + * xe_bo_vma_count_inc_locked() - Account a new VMA on a BO + * @bo: Buffer object + * + * Increments vma_count. + * + * Caller must hold the BO's dma-resv lock. + */ +static inline void xe_bo_vma_count_inc_locked(struct xe_bo *bo) +{ + xe_bo_assert_held(bo); + + if (drm_gem_is_imported(&bo->ttm.base)) + return; + + bo->purgeable.vma_count++; +} + +/** + * xe_bo_vma_count_dec_locked() - Account a VMA removal on a BO + * @bo: Buffer object + * + * Decrements vma_count. + * + * Caller must hold the BO's dma-resv lock. + */ +static inline void xe_bo_vma_count_dec_locked(struct xe_bo *bo) +{ + xe_bo_assert_held(bo); + + if (drm_gem_is_imported(&bo->ttm.base)) + return; + + xe_assert(xe_bo_device(bo), bo->purgeable.vma_count > 0); + bo->purgeable.vma_count--; +} + static inline void xe_bo_unpin_map_no_vm(struct xe_bo *bo) { if (likely(bo)) { diff --git a/drivers/gpu/drm/xe/xe_bo_types.h b/drivers/gpu/drm/xe/xe_bo_types.h index 9c199badd9b2..6756d7820aca 100644 --- a/drivers/gpu/drm/xe/xe_bo_types.h +++ b/drivers/gpu/drm/xe/xe_bo_types.h @@ -111,10 +111,31 @@ struct xe_bo { u64 min_align; /** - * @madv_purgeable: user space advise on BO purgeability, protected - * by BO's dma-resv lock. + * @purgeable: Purgeability state and accounting. + * + * All fields are protected by the BO's dma-resv lock. */ - u32 madv_purgeable; + struct { + /** + * @purgeable.state: BO purgeability state (WILLNEED/DONTNEED/PURGED). + */ + u32 state; + + /** + * @purgeable.vma_count: Number of VMAs currently mapping this BO. + */ + u32 vma_count; + + /** + * @purgeable.willneed_count: Number of active WILLNEED holders. + * + * Counts WILLNEED VMAs plus active dma-buf exports for + * non-imported BOs. The BO flips to DONTNEED on a 1->0 + * transition only when VMAs still exist; if the last VMA is + * removed, the previous BO state is preserved. + */ + u32 willneed_count; + } purgeable; }; #endif diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c index b9828da15897..855d32ba314d 100644 --- a/drivers/gpu/drm/xe/xe_dma_buf.c +++ b/drivers/gpu/drm/xe/xe_dma_buf.c @@ -193,6 +193,18 @@ static int xe_dma_buf_begin_cpu_access(struct dma_buf *dma_buf, return 0; } +static void xe_dma_buf_release(struct dma_buf *dmabuf) +{ + struct drm_gem_object *obj = dmabuf->priv; + struct xe_bo *bo = gem_to_xe_bo(obj); + + xe_bo_lock(bo, false); + xe_bo_willneed_put_locked(bo); + xe_bo_unlock(bo); + + drm_gem_dmabuf_release(dmabuf); +} + static const struct dma_buf_ops xe_dmabuf_ops = { .attach = xe_dma_buf_attach, .detach = xe_dma_buf_detach, @@ -200,7 +212,7 @@ static const struct dma_buf_ops xe_dmabuf_ops = { .unpin = xe_dma_buf_unpin, .map_dma_buf = xe_dma_buf_map, .unmap_dma_buf = xe_dma_buf_unmap, - .release = drm_gem_dmabuf_release, + .release = xe_dma_buf_release, .begin_cpu_access = xe_dma_buf_begin_cpu_access, .mmap = drm_gem_dmabuf_mmap, .vmap = drm_gem_dmabuf_vmap, @@ -241,18 +253,26 @@ struct dma_buf *xe_gem_prime_export(struct drm_gem_object *obj, int flags) ret = -EINVAL; goto out_unlock; } + + xe_bo_willneed_get_locked(bo); xe_bo_unlock(bo); ret = ttm_bo_setup_export(&bo->ttm, &ctx); if (ret) - return ERR_PTR(ret); + goto out_put; buf = drm_gem_prime_export(obj, flags); - if (!IS_ERR(buf)) - buf->ops = &xe_dmabuf_ops; + if (IS_ERR(buf)) { + ret = PTR_ERR(buf); + goto out_put; + } + buf->ops = &xe_dmabuf_ops; return buf; +out_put: + xe_bo_lock(bo, false); + xe_bo_willneed_put_locked(bo); out_unlock: xe_bo_unlock(bo); return ERR_PTR(ret); diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c index c3836f6eab35..12457173ba85 100644 --- a/drivers/gpu/drm/xe/xe_vm.c +++ b/drivers/gpu/drm/xe/xe_vm.c @@ -1131,6 +1131,10 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm, vma->gpuva.gem.offset = bo_offset_or_userptr; drm_gpuva_link(&vma->gpuva, vm_bo); drm_gpuvm_bo_put(vm_bo); + + xe_bo_vma_count_inc_locked(bo); + if (vma->attr.purgeable_state == XE_MADV_PURGEABLE_WILLNEED) + xe_bo_willneed_get_locked(bo);So at very top of this function I think: if (bo && attr->purgeable_state == XE_MADV_PURGEABLE_WILLNEED) { if (xe_bo_madv_is_dontneed(bo)) return ERR_PTR(-EBUSY); /* BO marked purgeable */ else if (xe_bo_is_purged(bo)) return ERR_PTR(-EINVAL); /* BO already purged */ } Then delete the check in vma_lock_and_validate. I think check in vma_lock_and_validate is actually wrong for rebinds too - e.g., it is prefectly to do a partial unbind a dontneed or purged BO and the existing check I believe would reject this.
Agreed. I will dropped .check_purged from MAP and REMAP prev/next in vm_bind_ioctl_op_lock_and_prep() for v3. The check now lives in xe_vma_create() and only triggers when attr->purgeable_state == WILLNEED, so partial unbind/rebind on DONTNEED or PURGED BOs works as expected. and PREFETCH keeps .check_purged as it is a separate check for existing VMAs with no backing store to migrate.
We should put together a test for for this too. addr = bind(2M); madvise(addr, DONTNEED); unbind(addr, 1M); Assuming the current code fails in this test case and new code works, I'd suggest making this patch a fixes too.
Noted. I will add a test case to cover this and include the appropriate fix tag
Matt} else /* userptr or null */ { if (!is_null && !is_cpu_addr_mirror) { struct xe_userptr_vma *uvma = to_userptr_vma(vma); @@ -1208,7 +1212,10 @@ static void xe_vma_destroy(struct xe_vma *vma, struct dma_fence *fence) xe_bo_assert_held(bo); drm_gpuva_unlink(&vma->gpuva); - xe_bo_recompute_purgeable_state(bo); + + xe_bo_vma_count_dec_locked(bo); + if (vma->attr.purgeable_state == XE_MADV_PURGEABLE_WILLNEED) + xe_bo_willneed_put_locked(bo); } xe_vm_assert_held(vm); diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c index c78906dea82b..c4fb29004195 100644 --- a/drivers/gpu/drm/xe/xe_vm_madvise.c +++ b/drivers/gpu/drm/xe/xe_vm_madvise.c @@ -185,147 +185,6 @@ static void madvise_pat_index(struct xe_device *xe, struct xe_vm *vm, } } -/** - * xe_bo_is_dmabuf_shared() - Check if BO is shared via dma-buf - * @bo: Buffer object - * - * Prevent marking imported or exported dma-bufs as purgeable. - * For imported BOs, Xe doesn't own the backing store and cannot - * safely reclaim pages (exporter or other devices may still be - * using them). For exported BOs, external devices may have active - * mappings we cannot track. - * - * Return: true if BO is imported or exported, false otherwise - */ -static bool xe_bo_is_dmabuf_shared(struct xe_bo *bo) -{ - struct drm_gem_object *obj = &bo->ttm.base; - - /* Imported: exporter owns backing store */ - if (drm_gem_is_imported(obj)) - return true; - - /* Exported: external devices may be accessing */ - if (obj->dma_buf) - return true; - - return false; -} - -/** - * enum xe_bo_vmas_purge_state - VMA purgeable state aggregation - * - * Distinguishes whether a BO's VMAs are all DONTNEED, have at least - * one WILLNEED, or have no VMAs at all. - * - * Enum values align with XE_MADV_PURGEABLE_* states for consistency. - */ -enum xe_bo_vmas_purge_state { - /** @XE_BO_VMAS_STATE_WILLNEED: At least one VMA is WILLNEED */ - XE_BO_VMAS_STATE_WILLNEED = 0, - /** @XE_BO_VMAS_STATE_DONTNEED: All VMAs are DONTNEED */ - XE_BO_VMAS_STATE_DONTNEED = 1, - /** @XE_BO_VMAS_STATE_NO_VMAS: BO has no VMAs */ - XE_BO_VMAS_STATE_NO_VMAS = 2, -}; - -/* - * xe_bo_recompute_purgeable_state() casts between xe_bo_vmas_purge_state and - * xe_madv_purgeable_state. Enforce that WILLNEED=0 and DONTNEED=1 match across - * both enums so the single-line cast is always valid. - */ -static_assert(XE_BO_VMAS_STATE_WILLNEED == (int)XE_MADV_PURGEABLE_WILLNEED, - "VMA purge state WILLNEED must equal madv purgeable WILLNEED"); -static_assert(XE_BO_VMAS_STATE_DONTNEED == (int)XE_MADV_PURGEABLE_DONTNEED, - "VMA purge state DONTNEED must equal madv purgeable DONTNEED"); - -/** - * xe_bo_all_vmas_dontneed() - Determine BO VMA purgeable state - * @bo: Buffer object - * - * Check all VMAs across all VMs to determine aggregate purgeable state. - * Shared BOs require unanimous DONTNEED state from all mappings. - * - * Caller must hold BO dma-resv lock. - * - * Return: XE_BO_VMAS_STATE_DONTNEED if all VMAs are DONTNEED, - * XE_BO_VMAS_STATE_WILLNEED if at least one VMA is not DONTNEED, - * XE_BO_VMAS_STATE_NO_VMAS if BO has no VMAs - */ -static enum xe_bo_vmas_purge_state xe_bo_all_vmas_dontneed(struct xe_bo *bo) -{ - struct drm_gpuvm_bo *vm_bo; - struct drm_gpuva *gpuva; - struct drm_gem_object *obj = &bo->ttm.base; - bool has_vmas = false; - - xe_bo_assert_held(bo); - - /* Shared dma-bufs cannot be purgeable */ - if (xe_bo_is_dmabuf_shared(bo)) - return XE_BO_VMAS_STATE_WILLNEED; - - drm_gem_for_each_gpuvm_bo(vm_bo, obj) { - drm_gpuvm_bo_for_each_va(gpuva, vm_bo) { - struct xe_vma *vma = gpuva_to_vma(gpuva); - - has_vmas = true; - - /* Any non-DONTNEED VMA prevents purging */ - if (vma->attr.purgeable_state != XE_MADV_PURGEABLE_DONTNEED) - return XE_BO_VMAS_STATE_WILLNEED; - } - } - - /* - * No VMAs => preserve existing BO purgeable state. - * Avoids incorrectly flipping DONTNEED -> WILLNEED when last VMA unmapped. - */ - if (!has_vmas) - return XE_BO_VMAS_STATE_NO_VMAS; - - return XE_BO_VMAS_STATE_DONTNEED; -} - -/** - * xe_bo_recompute_purgeable_state() - Recompute BO purgeable state from VMAs - * @bo: Buffer object - * - * Walk all VMAs to determine if BO should be purgeable or not. - * Shared BOs require unanimous DONTNEED state from all mappings. - * If the BO has no VMAs the existing state is preserved. - * - * Locking: Caller must hold BO dma-resv lock. When iterating GPUVM lists, - * VM lock must also be held (write) to prevent concurrent VMA modifications. - * This is satisfied at both call sites: - * - xe_vma_destroy(): holds vm->lock write - * - madvise_purgeable(): holds vm->lock write (from madvise ioctl path) - * - * Return: nothing - */ -void xe_bo_recompute_purgeable_state(struct xe_bo *bo) -{ - enum xe_bo_vmas_purge_state vma_state; - - if (!bo) - return; - - xe_bo_assert_held(bo); - - /* - * Once purged, always purged. Cannot transition back to WILLNEED. - * This matches i915 semantics where purged BOs are permanently invalid. - */ - if (bo->madv_purgeable == XE_MADV_PURGEABLE_PURGED) - return; - - vma_state = xe_bo_all_vmas_dontneed(bo); - - if (vma_state != (enum xe_bo_vmas_purge_state)bo->madv_purgeable && - vma_state != XE_BO_VMAS_STATE_NO_VMAS) - xe_bo_set_purgeable_state(bo, (enum xe_madv_purgeable_state)vma_state); -} - /** * madvise_purgeable - Handle purgeable buffer object advice * @xe: XE device @@ -359,12 +218,6 @@ static void madvise_purgeable(struct xe_device *xe, struct xe_vm *vm, /* BO must be locked before modifying madv state */ xe_bo_assert_held(bo); - /* Skip shared dma-bufs - no PTEs to zap */ - if (xe_bo_is_dmabuf_shared(bo)) { - vmas[i]->skip_invalidation = true; - continue; - } - /* * Once purged, always purged. Cannot transition back to WILLNEED. * This matches i915 semantics where purged BOs are permanently invalid. @@ -377,13 +230,14 @@ static void madvise_purgeable(struct xe_device *xe, struct xe_vm *vm, switch (op->purge_state_val.val) { case DRM_XE_VMA_PURGEABLE_STATE_WILLNEED: - vmas[i]->attr.purgeable_state = XE_MADV_PURGEABLE_WILLNEED; vmas[i]->skip_invalidation = true; - - xe_bo_recompute_purgeable_state(bo); + /* Only act on a real DONTNEED -> WILLNEED transition. */ + if (vmas[i]->attr.purgeable_state == XE_MADV_PURGEABLE_DONTNEED) { + vmas[i]->attr.purgeable_state = XE_MADV_PURGEABLE_WILLNEED; + xe_bo_willneed_get_locked(bo); + } break; case DRM_XE_VMA_PURGEABLE_STATE_DONTNEED: - vmas[i]->attr.purgeable_state = XE_MADV_PURGEABLE_DONTNEED; /* * Don't zap PTEs at DONTNEED time -- pages are still * alive. The zap happens in xe_bo_move_notify() right @@ -391,7 +245,11 @@ static void madvise_purgeable(struct xe_device *xe, struct xe_vm *vm, */ vmas[i]->skip_invalidation = true; - xe_bo_recompute_purgeable_state(bo); + /* Only act on a real WILLNEED -> DONTNEED transition. */ + if (vmas[i]->attr.purgeable_state == XE_MADV_PURGEABLE_WILLNEED) { + vmas[i]->attr.purgeable_state = XE_MADV_PURGEABLE_DONTNEED; + xe_bo_willneed_put_locked(bo); + } break; default: /* Should never hit - values validated in madvise_args_are_sane() */ diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.h b/drivers/gpu/drm/xe/xe_vm_madvise.h index 39acd2689ca0..a3078f634c7e 100644 --- a/drivers/gpu/drm/xe/xe_vm_madvise.h +++ b/drivers/gpu/drm/xe/xe_vm_madvise.h @@ -13,6 +13,4 @@ struct xe_bo; int xe_vm_madvise_ioctl(struct drm_device *dev, void *data, struct drm_file *file); -void xe_bo_recompute_purgeable_state(struct xe_bo *bo); - #endif -- 2.43.0