[Intel-xe] [PATCH] drm/xe: NULL binding implementation

Zanoni, Paulo R paulo.r.zanoni at intel.com
Fri Jun 16 17:33:45 UTC 2023


On Thu, 2023-06-15 at 11:34 -0700, Matthew Brost wrote:
> Add uAPI and implementation for NULL bindings. A NULL binding is defined
> as writes dropped and read zero. A single bit in the uAPI has been added
> which results in a single bit in the PTEs being set.
> 
> NULL bindings are intendedd to be used to implement VK sparse bindings,
> in particular residencyNonResidentStrict property.
> 
> v2: Fix BUG_ON shown in VK testing, fix check patch warning, fix
> xe_pt_scan_64K, update __gen8_pte_encode to understand NULL bindings,
> remove else if vma_addr

This seems to be working fine. I ran it through the dEQP sparse cases
with my branch and no regressions.

Tested-by: Paulo Zanoni <paulo.r.zanoni at intel.com>

Thanks a lot!

> 
> Suggested-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_bo.h           |  1 +
>  drivers/gpu/drm/xe/xe_exec.c         |  2 +
>  drivers/gpu/drm/xe/xe_gt_pagefault.c |  4 +-
>  drivers/gpu/drm/xe/xe_pt.c           | 54 ++++++++++-----
>  drivers/gpu/drm/xe/xe_vm.c           | 99 ++++++++++++++++++----------
>  drivers/gpu/drm/xe/xe_vm.h           | 12 +++-
>  drivers/gpu/drm/xe/xe_vm_types.h     |  1 +
>  include/uapi/drm/xe_drm.h            |  8 +++
>  8 files changed, 126 insertions(+), 55 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
> index dd3d448fee0b..3a148cc6e811 100644
> --- a/drivers/gpu/drm/xe/xe_bo.h
> +++ b/drivers/gpu/drm/xe/xe_bo.h
> @@ -61,6 +61,7 @@
>  #define XE_PPGTT_PTE_LM			BIT_ULL(11)
>  #define XE_PDE_64K			BIT_ULL(6)
>  #define XE_PTE_PS64			BIT_ULL(8)
> +#define XE_PTE_NULL			BIT_ULL(9)
>  
>  #define XE_PAGE_PRESENT			BIT_ULL(0)
>  #define XE_PAGE_RW			BIT_ULL(1)
> diff --git a/drivers/gpu/drm/xe/xe_exec.c b/drivers/gpu/drm/xe/xe_exec.c
> index e44076ee2e11..4f7694a29348 100644
> --- a/drivers/gpu/drm/xe/xe_exec.c
> +++ b/drivers/gpu/drm/xe/xe_exec.c
> @@ -120,6 +120,8 @@ static int xe_exec_begin(struct xe_engine *e, struct ww_acquire_ctx *ww,
>  	 * to a location where the GPU can access it).
>  	 */
>  	list_for_each_entry(vma, &vm->rebind_list, rebind_link) {
> +		XE_WARN_ON(xe_vma_is_null(vma));
> +
>  		if (xe_vma_is_userptr(vma))
>  			continue;
>  
> diff --git a/drivers/gpu/drm/xe/xe_gt_pagefault.c b/drivers/gpu/drm/xe/xe_gt_pagefault.c
> index 73db7f7c0381..6faebd02f3fb 100644
> --- a/drivers/gpu/drm/xe/xe_gt_pagefault.c
> +++ b/drivers/gpu/drm/xe/xe_gt_pagefault.c
> @@ -533,8 +533,8 @@ static int handle_acc(struct xe_gt *gt, struct acc *acc)
>  
>  	trace_xe_vma_acc(vma);
>  
> -	/* Userptr can't be migrated, nothing to do */
> -	if (xe_vma_is_userptr(vma))
> +	/* Userptr or null can't be migrated, nothing to do */
> +	if (xe_vma_has_no_bo(vma))
>  		goto unlock_vm;
>  
>  	/* Lock VM and BOs dma-resv */
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index 29c1b1f0bd7c..fe1c77b139e4 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -81,6 +81,9 @@ u64 xe_pde_encode(struct xe_bo *bo, u64 bo_offset,
>  static dma_addr_t vma_addr(struct xe_vma *vma, u64 offset,
>  			   size_t page_size, bool *is_vram)
>  {
> +	if (xe_vma_is_null(vma))
> +		return 0;
> +
>  	if (xe_vma_is_userptr(vma)) {
>  		struct xe_res_cursor cur;
>  		u64 page;
> @@ -105,6 +108,9 @@ static u64 __pte_encode(u64 pte, enum xe_cache_level cache, u32 flags,
>  	if (unlikely(flags & XE_PTE_FLAG_READ_ONLY))
>  		pte &= ~XE_PAGE_RW;
>  
> +	if (unlikely(flags & XE_PTE_FLAG_NULL))
> +		pte |= XE_PTE_NULL;
> +
>  	/* FIXME: I don't think the PPAT handling is correct for MTL */
>  
>  	switch (cache) {
> @@ -557,6 +563,10 @@ static bool xe_pt_hugepte_possible(u64 addr, u64 next, unsigned int level,
>  	if (next - xe_walk->va_curs_start > xe_walk->curs->size)
>  		return false;
>  
> +	/* null VMA's do not have dma addresses */
> +	if (xe_walk->pte_flags & XE_PTE_FLAG_NULL)
> +		return true;
> +
>  	/* Is the DMA address huge PTE size aligned? */
>  	size = next - addr;
>  	dma = addr - xe_walk->va_curs_start + xe_res_dma(xe_walk->curs);
> @@ -579,6 +589,10 @@ xe_pt_scan_64K(u64 addr, u64 next, struct xe_pt_stage_bind_walk *xe_walk)
>  	if (next > xe_walk->l0_end_addr)
>  		return false;
>  
> +	/* null VMA's do not have dma addresses */
> +	if (xe_walk->pte_flags & XE_PTE_FLAG_NULL)
> +		return true;
> +
>  	xe_res_next(&curs, addr - xe_walk->va_curs_start);
>  	for (; addr < next; addr += SZ_64K) {
>  		if (!IS_ALIGNED(xe_res_dma(&curs), SZ_64K) || curs.size < SZ_64K)
> @@ -629,10 +643,12 @@ xe_pt_stage_bind_entry(struct xe_ptw *parent, pgoff_t offset,
>  	/* Is this a leaf entry ?*/
>  	if (level == 0 || xe_pt_hugepte_possible(addr, next, level, xe_walk)) {
>  		struct xe_res_cursor *curs = xe_walk->curs;
> +		bool is_null = xe_walk->pte_flags & XE_PTE_FLAG_NULL;
>  
>  		XE_WARN_ON(xe_walk->va_curs_start != addr);
>  
> -		pte = __pte_encode(xe_res_dma(curs) + xe_walk->dma_offset,
> +		pte = __pte_encode(is_null ? 0 :
> +				   xe_res_dma(curs) + xe_walk->dma_offset,
>  				   xe_walk->cache, xe_walk->pte_flags,
>  				   level);
>  		pte |= xe_walk->default_pte;
> @@ -652,7 +668,8 @@ xe_pt_stage_bind_entry(struct xe_ptw *parent, pgoff_t offset,
>  		if (unlikely(ret))
>  			return ret;
>  
> -		xe_res_next(curs, next - addr);
> +		if (!is_null)
> +			xe_res_next(curs, next - addr);
>  		xe_walk->va_curs_start = next;
>  		*action = ACTION_CONTINUE;
>  
> @@ -759,24 +776,29 @@ xe_pt_stage_bind(struct xe_tile *tile, struct xe_vma *vma,
>  		xe_walk.dma_offset = vram_region_gpu_offset(bo->ttm.resource);
>  		xe_walk.cache = XE_CACHE_WB;
>  	} else {
> -		if (!xe_vma_is_userptr(vma) && bo->flags & XE_BO_SCANOUT_BIT)
> +		if (!xe_vma_has_no_bo(vma) && bo->flags & XE_BO_SCANOUT_BIT)
>  			xe_walk.cache = XE_CACHE_WT;
>  		else
>  			xe_walk.cache = XE_CACHE_WB;
>  	}
> -	if (!xe_vma_is_userptr(vma) && xe_bo_is_stolen(bo))
> +	if (!xe_vma_has_no_bo(vma) && xe_bo_is_stolen(bo))
>  		xe_walk.dma_offset = xe_ttm_stolen_gpu_offset(xe_bo_device(bo));
>  
>  	xe_bo_assert_held(bo);
> -	if (xe_vma_is_userptr(vma))
> -		xe_res_first_sg(vma->userptr.sg, 0, vma->end - vma->start + 1,
> -				&curs);
> -	else if (xe_bo_is_vram(bo) || xe_bo_is_stolen(bo))
> -		xe_res_first(bo->ttm.resource, vma->bo_offset,
> -			     vma->end - vma->start + 1, &curs);
> -	else
> -		xe_res_first_sg(xe_bo_get_sg(bo), vma->bo_offset,
> -				vma->end - vma->start + 1, &curs);
> +
> +	if (!xe_vma_is_null(vma)) {
> +		if (xe_vma_is_userptr(vma))
> +			xe_res_first_sg(vma->userptr.sg, 0,
> +					vma->end - vma->start + 1, &curs);
> +		else if (xe_bo_is_vram(bo) || xe_bo_is_stolen(bo))
> +			xe_res_first(bo->ttm.resource, vma->bo_offset,
> +				     vma->end - vma->start + 1, &curs);
> +		else
> +			xe_res_first_sg(xe_bo_get_sg(bo), vma->bo_offset,
> +					vma->end - vma->start + 1, &curs);
> +	} else {
> +		curs.size = vma->end - vma->start + 1;
> +	}
>  
>  	ret = xe_pt_walk_range(&pt->base, pt->level, vma->start, vma->end + 1,
>  				&xe_walk.base);
> @@ -965,7 +987,7 @@ static void xe_pt_commit_locks_assert(struct xe_vma *vma)
>  
>  	if (xe_vma_is_userptr(vma))
>  		lockdep_assert_held_read(&vm->userptr.notifier_lock);
> -	else
> +	else if (!xe_vma_is_null(vma))
>  		dma_resv_assert_held(vma->bo->ttm.base.resv);
>  
>  	dma_resv_assert_held(&vm->resv);
> @@ -1341,7 +1363,7 @@ __xe_pt_bind_vma(struct xe_tile *tile, struct xe_vma *vma, struct xe_engine *e,
>  				   DMA_RESV_USAGE_KERNEL :
>  				   DMA_RESV_USAGE_BOOKKEEP);
>  
> -		if (!xe_vma_is_userptr(vma) && !vma->bo->vm)
> +		if (!xe_vma_has_no_bo(vma) && !vma->bo->vm)
>  			dma_resv_add_fence(vma->bo->ttm.base.resv, fence,
>  					   DMA_RESV_USAGE_BOOKKEEP);
>  		xe_pt_commit_bind(vma, entries, num_entries, rebind,
> @@ -1658,7 +1680,7 @@ __xe_pt_unbind_vma(struct xe_tile *tile, struct xe_vma *vma, struct xe_engine *e
>  				   DMA_RESV_USAGE_BOOKKEEP);
>  
>  		/* This fence will be installed by caller when doing eviction */
> -		if (!xe_vma_is_userptr(vma) && !vma->bo->vm)
> +		if (!xe_vma_has_no_bo(vma) && !vma->bo->vm)
>  			dma_resv_add_fence(vma->bo->ttm.base.resv, fence,
>  					   DMA_RESV_USAGE_BOOKKEEP);
>  		xe_pt_commit_unbind(vma, entries, num_entries,
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 56ed2cb75c8e..113853d496c7 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -590,7 +590,7 @@ static void preempt_rebind_work_func(struct work_struct *w)
>  		goto out_unlock;
>  
>  	list_for_each_entry(vma, &vm->rebind_list, rebind_link) {
> -		if (xe_vma_is_userptr(vma) || vma->destroyed)
> +		if (xe_vma_has_no_bo(vma) || vma->destroyed)
>  			continue;
>  
>  		err = xe_bo_validate(vma->bo, vm, false);
> @@ -843,6 +843,7 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
>  				    u64 bo_offset_or_userptr,
>  				    u64 start, u64 end,
>  				    bool read_only,
> +				    bool is_null,
>  				    u64 tile_mask)
>  {
>  	struct xe_vma *vma;
> @@ -868,8 +869,11 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
>  	vma->vm = vm;
>  	vma->start = start;
>  	vma->end = end;
> +	vma->pte_flags = 0;
>  	if (read_only)
> -		vma->pte_flags = XE_PTE_FLAG_READ_ONLY;
> +		vma->pte_flags |= XE_PTE_FLAG_READ_ONLY;
> +	if (is_null)
> +		vma->pte_flags |= XE_PTE_FLAG_NULL;
>  
>  	if (tile_mask) {
>  		vma->tile_mask = tile_mask;
> @@ -886,23 +890,26 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
>  		vma->bo_offset = bo_offset_or_userptr;
>  		vma->bo = xe_bo_get(bo);
>  		list_add_tail(&vma->bo_link, &bo->vmas);
> -	} else /* userptr */ {
> -		u64 size = end - start + 1;
> -		int err;
> +	} else /* userptr or null */ {
> +		if (!is_null) {
> +			u64 size = end - start + 1;
> +			int err;
>  
> -		vma->userptr.ptr = bo_offset_or_userptr;
> +			vma->userptr.ptr = bo_offset_or_userptr;
>  
> -		err = mmu_interval_notifier_insert(&vma->userptr.notifier,
> -						   current->mm,
> -						   vma->userptr.ptr, size,
> -						   &vma_userptr_notifier_ops);
> -		if (err) {
> -			kfree(vma);
> -			vma = ERR_PTR(err);
> -			return vma;
> +			err = mmu_interval_notifier_insert(&vma->userptr.notifier,
> +							   current->mm,
> +							   vma->userptr.ptr, size,
> +							   &vma_userptr_notifier_ops);
> +			if (err) {
> +				kfree(vma);
> +				vma = ERR_PTR(err);
> +				return vma;
> +			}
> +
> +			vma->userptr.notifier_seq = LONG_MAX;
>  		}
>  
> -		vma->userptr.notifier_seq = LONG_MAX;
>  		xe_vm_get(vm);
>  	}
>  
> @@ -942,6 +949,8 @@ static void xe_vma_destroy_late(struct xe_vma *vma)
>  		 */
>  		mmu_interval_notifier_remove(&vma->userptr.notifier);
>  		xe_vm_put(vm);
> +	} else if (xe_vma_is_null(vma)) {
> +		xe_vm_put(vm);
>  	} else {
>  		xe_bo_put(vma->bo);
>  	}
> @@ -1024,7 +1033,7 @@ static void xe_vma_destroy(struct xe_vma *vma, struct dma_fence *fence)
>  		list_del_init(&vma->userptr.invalidate_link);
>  		spin_unlock(&vm->userptr.invalidated_lock);
>  		list_del(&vma->userptr_link);
> -	} else {
> +	} else if (!xe_vma_is_null(vma)) {
>  		xe_bo_assert_held(vma->bo);
>  		list_del(&vma->bo_link);
>  
> @@ -1393,7 +1402,7 @@ void xe_vm_close_and_put(struct xe_vm *vm)
>  	while (vm->vmas.rb_node) {
>  		struct xe_vma *vma = to_xe_vma(vm->vmas.rb_node);
>  
> -		if (xe_vma_is_userptr(vma)) {
> +		if (xe_vma_has_no_bo(vma)) {
>  			down_read(&vm->userptr.notifier_lock);
>  			vma->destroyed = true;
>  			up_read(&vm->userptr.notifier_lock);
> @@ -1402,7 +1411,7 @@ void xe_vm_close_and_put(struct xe_vm *vm)
>  		rb_erase(&vma->vm_node, &vm->vmas);
>  
>  		/* easy case, remove from VMA? */
> -		if (xe_vma_is_userptr(vma) || vma->bo->vm) {
> +		if (xe_vma_has_no_bo(vma) || vma->bo->vm) {
>  			xe_vma_destroy(vma, NULL);
>  			continue;
>  		}
> @@ -2036,7 +2045,7 @@ static int xe_vm_prefetch(struct xe_vm *vm, struct xe_vma *vma,
>  
>  	XE_BUG_ON(region > ARRAY_SIZE(region_to_mem_type));
>  
> -	if (!xe_vma_is_userptr(vma)) {
> +	if (!xe_vma_has_no_bo(vma)) {
>  		err = xe_bo_migrate(vma->bo, region_to_mem_type[region]);
>  		if (err)
>  			return err;
> @@ -2645,6 +2654,8 @@ static struct xe_vma *vm_unbind_lookup_vmas(struct xe_vm *vm,
>  					  lookup->start - 1,
>  					  (first->pte_flags &
>  					   XE_PTE_FLAG_READ_ONLY),
> +					  (first->pte_flags &
> +					   XE_PTE_FLAG_NULL),
>  					  first->tile_mask);
>  		if (first->bo)
>  			xe_bo_unlock(first->bo, &ww);
> @@ -2652,7 +2663,7 @@ static struct xe_vma *vm_unbind_lookup_vmas(struct xe_vm *vm,
>  			err = -ENOMEM;
>  			goto unwind;
>  		}
> -		if (!first->bo) {
> +		if (xe_vma_is_userptr(first)) {
>  			err = xe_vma_userptr_pin_pages(new_first);
>  			if (err)
>  				goto unwind;
> @@ -2677,6 +2688,7 @@ static struct xe_vma *vm_unbind_lookup_vmas(struct xe_vm *vm,
>  					 last->end,
>  					 (last->pte_flags &
>  					  XE_PTE_FLAG_READ_ONLY),
> +					 (last->pte_flags & XE_PTE_FLAG_NULL),
>  					 last->tile_mask);
>  		if (last->bo)
>  			xe_bo_unlock(last->bo, &ww);
> @@ -2684,7 +2696,7 @@ static struct xe_vma *vm_unbind_lookup_vmas(struct xe_vm *vm,
>  			err = -ENOMEM;
>  			goto unwind;
>  		}
> -		if (!last->bo) {
> +		if (xe_vma_is_userptr(last)) {
>  			err = xe_vma_userptr_pin_pages(new_last);
>  			if (err)
>  				goto unwind;
> @@ -2744,7 +2756,7 @@ static struct xe_vma *vm_prefetch_lookup_vmas(struct xe_vm *vm,
>  		      *next;
>  	struct rb_node *node;
>  
> -	if (!xe_vma_is_userptr(vma)) {
> +	if (!xe_vma_has_no_bo(vma)) {
>  		if (!xe_bo_can_migrate(vma->bo, region_to_mem_type[region]))
>  			return ERR_PTR(-EINVAL);
>  	}
> @@ -2753,7 +2765,7 @@ static struct xe_vma *vm_prefetch_lookup_vmas(struct xe_vm *vm,
>  	while ((node = rb_next(node))) {
>  		if (!xe_vma_cmp_vma_cb(lookup, node)) {
>  			__vma = to_xe_vma(node);
> -			if (!xe_vma_is_userptr(__vma)) {
> +			if (!xe_vma_has_no_bo(__vma)) {
>  				if (!xe_bo_can_migrate(__vma->bo, region_to_mem_type[region]))
>  					goto flush_list;
>  			}
> @@ -2767,7 +2779,7 @@ static struct xe_vma *vm_prefetch_lookup_vmas(struct xe_vm *vm,
>  	while ((node = rb_prev(node))) {
>  		if (!xe_vma_cmp_vma_cb(lookup, node)) {
>  			__vma = to_xe_vma(node);
> -			if (!xe_vma_is_userptr(__vma)) {
> +			if (!xe_vma_has_no_bo(__vma)) {
>  				if (!xe_bo_can_migrate(__vma->bo, region_to_mem_type[region]))
>  					goto flush_list;
>  			}
> @@ -2826,21 +2838,23 @@ static struct xe_vma *vm_bind_ioctl_lookup_vma(struct xe_vm *vm,
>  
>  	switch (VM_BIND_OP(op)) {
>  	case XE_VM_BIND_OP_MAP:
> -		XE_BUG_ON(!bo);
> -
> -		err = xe_bo_lock(bo, &ww, 0, true);
> -		if (err)
> -			return ERR_PTR(err);
> +		if (bo) {
> +			err = xe_bo_lock(bo, &ww, 0, true);
> +			if (err)
> +				return ERR_PTR(err);
> +		}
>  		vma = xe_vma_create(vm, bo, bo_offset_or_userptr, addr,
>  				    addr + range - 1,
>  				    op & XE_VM_BIND_FLAG_READONLY,
> +				    op & XE_VM_BIND_FLAG_NULL,
>  				    tile_mask);
> -		xe_bo_unlock(bo, &ww);
> +		if (bo)
> +			xe_bo_unlock(bo, &ww);
>  		if (!vma)
>  			return ERR_PTR(-ENOMEM);
>  
>  		xe_vm_insert_vma(vm, vma);
> -		if (!bo->vm) {
> +		if (bo && !bo->vm) {
>  			vm_insert_extobj(vm, vma);
>  			err = add_preempt_fences(vm, bo);
>  			if (err) {
> @@ -2874,6 +2888,7 @@ static struct xe_vma *vm_bind_ioctl_lookup_vma(struct xe_vm *vm,
>  		vma = xe_vma_create(vm, NULL, bo_offset_or_userptr, addr,
>  				    addr + range - 1,
>  				    op & XE_VM_BIND_FLAG_READONLY,
> +				    op & XE_VM_BIND_FLAG_NULL,
>  				    tile_mask);
>  		if (!vma)
>  			return ERR_PTR(-ENOMEM);
> @@ -2899,11 +2914,12 @@ static struct xe_vma *vm_bind_ioctl_lookup_vma(struct xe_vm *vm,
>  #ifdef TEST_VM_ASYNC_OPS_ERROR
>  #define SUPPORTED_FLAGS	\
>  	(FORCE_ASYNC_OP_ERROR | XE_VM_BIND_FLAG_ASYNC | \
> -	 XE_VM_BIND_FLAG_READONLY | XE_VM_BIND_FLAG_IMMEDIATE | 0xffff)
> +	 XE_VM_BIND_FLAG_READONLY | XE_VM_BIND_FLAG_IMMEDIATE | \
> +	 XE_VM_BIND_FLAG_NULL | 0xffff)
>  #else
>  #define SUPPORTED_FLAGS	\
>  	(XE_VM_BIND_FLAG_ASYNC | XE_VM_BIND_FLAG_READONLY | \
> -	 XE_VM_BIND_FLAG_IMMEDIATE | 0xffff)
> +	 XE_VM_BIND_FLAG_IMMEDIATE | XE_VM_BIND_FLAG_NULL | 0xffff)
>  #endif
>  #define XE_64K_PAGE_MASK 0xffffull
>  
> @@ -2951,6 +2967,7 @@ static int vm_bind_ioctl_check_args(struct xe_device *xe,
>  		u32 obj = (*bind_ops)[i].obj;
>  		u64 obj_offset = (*bind_ops)[i].obj_offset;
>  		u32 region = (*bind_ops)[i].region;
> +		bool is_null = op &  XE_VM_BIND_FLAG_NULL;
>  
>  		if (XE_IOCTL_ERR(xe, (*bind_ops)[i].pad) ||
>  		    XE_IOCTL_ERR(xe, (*bind_ops)[i].reserved[0] ||
> @@ -2984,8 +3001,13 @@ static int vm_bind_ioctl_check_args(struct xe_device *xe,
>  		if (XE_IOCTL_ERR(xe, VM_BIND_OP(op) >
>  				 XE_VM_BIND_OP_PREFETCH) ||
>  		    XE_IOCTL_ERR(xe, op & ~SUPPORTED_FLAGS) ||
> +		    XE_IOCTL_ERR(xe, obj && is_null) ||
> +		    XE_IOCTL_ERR(xe, obj_offset && is_null) ||
> +		    XE_IOCTL_ERR(xe, VM_BIND_OP(op) != XE_VM_BIND_OP_MAP &&
> +				 is_null) ||
>  		    XE_IOCTL_ERR(xe, !obj &&
> -				 VM_BIND_OP(op) == XE_VM_BIND_OP_MAP) ||
> +				 VM_BIND_OP(op) == XE_VM_BIND_OP_MAP &&
> +				 !is_null) ||
>  		    XE_IOCTL_ERR(xe, !obj &&
>  				 VM_BIND_OP(op) == XE_VM_BIND_OP_UNMAP_ALL) ||
>  		    XE_IOCTL_ERR(xe, addr &&
> @@ -3390,6 +3412,7 @@ int xe_vm_invalidate_vma(struct xe_vma *vma)
>  	int ret;
>  
>  	XE_BUG_ON(!xe_vm_in_fault_mode(vma->vm));
> +	XE_WARN_ON(xe_vma_is_null(vma));
>  	trace_xe_vma_usm_invalidate(vma);
>  
>  	/* Check that we don't race with page-table updates */
> @@ -3452,8 +3475,11 @@ int xe_analyze_vm(struct drm_printer *p, struct xe_vm *vm, int gt_id)
>  	for (node = rb_first(&vm->vmas); node; node = rb_next(node)) {
>  		struct xe_vma *vma = to_xe_vma(node);
>  		bool is_userptr = xe_vma_is_userptr(vma);
> +		bool is_null = xe_vma_is_null(vma);
>  
> -		if (is_userptr) {
> +		if (is_null) {
> +			addr = 0;
> +		} else if (is_userptr) {
>  			struct xe_res_cursor cur;
>  
>  			if (vma->userptr.sg) {
> @@ -3468,7 +3494,8 @@ int xe_analyze_vm(struct drm_printer *p, struct xe_vm *vm, int gt_id)
>  		}
>  		drm_printf(p, " [%016llx-%016llx] S:0x%016llx A:%016llx %s\n",
>  			   vma->start, vma->end, vma->end - vma->start + 1ull,
> -			   addr, is_userptr ? "USR" : is_vram ? "VRAM" : "SYS");
> +			   addr, is_null ? "NULL" : is_userptr ? "USR" :
> +			   is_vram ? "VRAM" : "SYS");
>  	}
>  	up_read(&vm->lock);
>  
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index bb2996856841..5edb7771629c 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -115,11 +115,21 @@ static inline void xe_vm_reactivate_rebind(struct xe_vm *vm)
>  	}
>  }
>  
> -static inline bool xe_vma_is_userptr(struct xe_vma *vma)
> +static inline bool xe_vma_is_null(struct xe_vma *vma)
> +{
> +	return vma->pte_flags & XE_PTE_FLAG_NULL;
> +}
> +
> +static inline bool xe_vma_has_no_bo(struct xe_vma *vma)
>  {
>  	return !vma->bo;
>  }
>  
> +static inline bool xe_vma_is_userptr(struct xe_vma *vma)
> +{
> +	return xe_vma_has_no_bo(vma) && !xe_vma_is_null(vma);
> +}
> +
>  int xe_vma_userptr_pin_pages(struct xe_vma *vma);
>  
>  int xe_vma_userptr_check_repin(struct xe_vma *vma);
> diff --git a/drivers/gpu/drm/xe/xe_vm_types.h b/drivers/gpu/drm/xe/xe_vm_types.h
> index a51e84e584b4..9b39c5f64afa 100644
> --- a/drivers/gpu/drm/xe/xe_vm_types.h
> +++ b/drivers/gpu/drm/xe/xe_vm_types.h
> @@ -31,6 +31,7 @@ struct xe_vma {
>  	u64 end;
>  	/** @pte_flags: pte flags for this VMA */
>  #define XE_PTE_FLAG_READ_ONLY		BIT(0)
> +#define XE_PTE_FLAG_NULL		BIT(1)
>  	u32 pte_flags;
>  
>  	/** @bo: BO if not a userptr, must be NULL is userptr */
> diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
> index 7f9a5849e88b..9bdea8b81435 100644
> --- a/include/uapi/drm/xe_drm.h
> +++ b/include/uapi/drm/xe_drm.h
> @@ -418,6 +418,14 @@ struct drm_xe_vm_bind_op {
>  	 * than differing the MAP to the page fault handler.
>  	 */
>  #define XE_VM_BIND_FLAG_IMMEDIATE	(0x1 << 18)
> +	/*
> +	 * When the NULL flag is set, the page tables are setup with a special
> +	 * bit which indicates writes are dropped and all reads return zero.  In
> +	 * the future, the NULL flags will only be valid for XE_VM_BIND_OP_MAP
> +	 * operations, the BO handle MBZ, and the BO offset MBZ. This flag is
> +	 * intended to implement VK sparse bindings.
> +	 */
> +#define XE_VM_BIND_FLAG_NULL		(0x1 << 19)
>  
>  	/** @reserved: Reserved */
>  	__u64 reserved[2];



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