[PATCH v3 1/2] drm/xe: Add xe_vm_has_valid_gpu_mapping helper
Ghimiray, Himal Prasad
himal.prasad.ghimiray at intel.com
Tue Jun 17 17:41:40 UTC 2025
On 16-06-2025 12:00, Matthew Brost wrote:
> Rather than having multiple READ_ONCE of the tile_* fields and comments
> in code, use helper with kernel doc for single access point and clear
> rules.
>
> v3:
> - s/xe_vm_has_valid_gpu_pages/xe_vm_has_valid_gpu_mapping
>
> Suggested-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
> drivers/gpu/drm/xe/xe_gt_pagefault.c | 9 ++-------
> drivers/gpu/drm/xe/xe_pt.c | 6 +++---
> drivers/gpu/drm/xe/xe_svm.c | 16 +++++++---------
> drivers/gpu/drm/xe/xe_vm.c | 2 +-
> drivers/gpu/drm/xe/xe_vm.h | 19 +++++++++++++++++++
> 5 files changed, 32 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_gt_pagefault.c b/drivers/gpu/drm/xe/xe_gt_pagefault.c
> index e2d975b2fddb..3522865c67c9 100644
> --- a/drivers/gpu/drm/xe/xe_gt_pagefault.c
> +++ b/drivers/gpu/drm/xe/xe_gt_pagefault.c
> @@ -69,15 +69,10 @@ static bool access_is_atomic(enum access_type access_type)
>
> static bool vma_is_valid(struct xe_tile *tile, struct xe_vma *vma)
> {
> - /*
> - * Advisory only check whether the VMA currently has a valid mapping,
> - * READ_ONCE pairs with WRITE_ONCE in xe_pt.c
> - */
> - return BIT(tile->id) & READ_ONCE(vma->tile_present) &&
> - !(BIT(tile->id) & READ_ONCE(vma->tile_invalidated));
> + return xe_vm_has_valid_gpu_mapping(tile, vma->tile_present,
> + vma->tile_invalidated);
> }
>
> -
> static int xe_pf_begin(struct drm_exec *exec, struct xe_vma *vma,
> bool atomic, unsigned int id)
> {
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index f39d5cc9f411..9c30111e8786 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -2196,7 +2196,7 @@ static void bind_op_commit(struct xe_vm *vm, struct xe_tile *tile,
> DMA_RESV_USAGE_KERNEL :
> DMA_RESV_USAGE_BOOKKEEP);
> }
> - /* All WRITE_ONCE pair with READ_ONCE in xe_gt_pagefault.c */
> + /* All WRITE_ONCE pair with READ_ONCE in xe_vm_has_valid_gpu_mapping() */
> WRITE_ONCE(vma->tile_present, vma->tile_present | BIT(tile->id));
> if (invalidate_on_bind)
> WRITE_ONCE(vma->tile_invalidated,
> @@ -2255,7 +2255,7 @@ static void range_present_and_invalidated_tile(struct xe_vm *vm,
> struct xe_svm_range *range,
> u8 tile_id)
> {
> - /* WRITE_ONCE pairs with READ_ONCE in xe_svm.c */
> + /* All WRITE_ONCE pair with READ_ONCE in xe_vm_has_valid_gpu_mapping() */
>
> lockdep_assert_held(&vm->svm.gpusvm.notifier_lock);
>
> @@ -2324,7 +2324,7 @@ static void op_commit(struct xe_vm *vm,
> }
> case DRM_GPUVA_OP_DRIVER:
> {
> - /* WRITE_ONCE pairs with READ_ONCE in xe_svm.c */
> + /* WRITE_ONCE pairs with READ_ONCE in xe_vm_has_valid_gpu_mapping() */
> if (op->subop == XE_VMA_SUBOP_MAP_RANGE)
> range_present_and_invalidated_tile(vm, op->map_range.range, tile->id);
> else if (op->subop == XE_VMA_SUBOP_UNMAP_RANGE)
> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
> index 2fbbd6a604ea..26418e9bdff0 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -141,7 +141,10 @@ xe_svm_range_notifier_event_begin(struct xe_vm *vm, struct drm_gpusvm_range *r,
> for_each_tile(tile, xe, id)
> if (xe_pt_zap_ptes_range(tile, vm, range)) {
> tile_mask |= BIT(id);
> - /* Pairs with READ_ONCE in xe_svm_range_is_valid */
> + /*
> + * WRITE_ONCE pairs with READ_ONCE in
> + * xe_vm_has_valid_gpu_mapping()
> + */
> WRITE_ONCE(range->tile_invalidated,
> range->tile_invalidated | BIT(id));
> }
> @@ -605,14 +608,9 @@ static bool xe_svm_range_is_valid(struct xe_svm_range *range,
> struct xe_tile *tile,
> bool devmem_only)
> {
> - /*
> - * Advisory only check whether the range currently has a valid mapping,
> - * READ_ONCE pairs with WRITE_ONCE in xe_pt.c,
> - * xe_svm_range_notifier_event_begin
> - */
> - return ((READ_ONCE(range->tile_present) &
> - ~READ_ONCE(range->tile_invalidated)) & BIT(tile->id)) &&
> - (!devmem_only || xe_svm_range_in_vram(range));
> + return (xe_vm_has_valid_gpu_mapping(tile, range->tile_present,
> + range->tile_invalidated) &&
> + (!devmem_only || xe_svm_range_in_vram(range)));
> }
>
> /** xe_svm_range_migrate_to_smem() - Move range pages from VRAM to SMEM
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 6ef8c4dab647..04d1a43b81e3 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -3961,7 +3961,7 @@ int xe_vm_invalidate_vma(struct xe_vma *vma)
> ret = xe_vm_range_tilemask_tlb_invalidation(xe_vma_vm(vma), xe_vma_start(vma),
> xe_vma_end(vma), tile_mask);
>
> - /* WRITE_ONCE pair with READ_ONCE in xe_gt_pagefault.c */
> + /* WRITE_ONCE pairs with READ_ONCE in xe_vm_has_valid_gpu_mapping() */
> WRITE_ONCE(vma->tile_invalidated, vma->tile_mask);
>
> return ret;
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index acd3fd6c605b..cc332c4ebdf2 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -375,6 +375,25 @@ static inline bool xe_vm_is_validating(struct xe_vm *vm)
> return false;
> }
>
> +/**
> + * xe_vm_has_valid_gpu_mapping() - Advisory helper to check if VMA or SVM range has
Nit the helper is no more in use for VMA in Patch 2.
Rest all looks good to me.
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
> + * a valid GPU mapping
> + * @tile: The tile which the GPU mapping belongs to
> + * @tile_present: Tile present mask
> + * @tile_invalidated: Tile invalidated mask
> + *
> + * The READ_ONCEs pair with WRITE_ONCEs in either the TLB invalidation paths
> + * (xe_vm.c, xe_svm.c) or the binding paths (xe_pt.c). These are not reliable
> + * without the notifier lock in userptr or SVM cases, and not reliable without
> + * the BO dma-resv lock in the BO case. As such, they should only be used in
> + * opportunistic cases (e.g., skipping a page fault fix or not skipping a TLB
> + * invalidation) where it is harmless.
> + *
> + * Return: True is there are valid GPU pages, False otherwise
> + */
> +#define xe_vm_has_valid_gpu_mapping(tile, tile_present, tile_invalidated) \
> + ((READ_ONCE(tile_present) & ~READ_ONCE(tile_invalidated)) & BIT(tile->id))
> +
> #if IS_ENABLED(CONFIG_DRM_XE_USERPTR_INVAL_INJECT)
> void xe_vma_userptr_force_invalidate(struct xe_userptr_vma *uvma);
> #else
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