Re: [PATCH v2 23/29] drm/xe: Add BO flags required for SVM

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Tue, 2024-10-15 at 20:25 -0700, Matthew Brost wrote:
> Add XE_BO_FLAG_SYSTEM_ALLOC to indicate BO is tied to SVM range.
> 
> Add XE_BO_FLAG_SKIP_CLEAR to indicate BO does not need to cleared.
> 
> v2:
>  - Take VM ref for system allocator BOs
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_bo.c | 15 +++++++++------
>  drivers/gpu/drm/xe/xe_bo.h |  2 ++
>  2 files changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> index a02d63e322ae..dbd03383878e 100644
> --- a/drivers/gpu/drm/xe/xe_bo.c
> +++ b/drivers/gpu/drm/xe/xe_bo.c
> @@ -685,8 +685,9 @@ static int xe_bo_move(struct ttm_buffer_object
> *ttm_bo, bool evict,
>  	move_lacks_source = !old_mem || (handle_system_ccs ? (!bo-
> >ccs_cleared) :
>  					
> (!mem_type_is_vram(old_mem_type) && !tt_has_data));
>  
> -	needs_clear = (ttm && ttm->page_flags &
> TTM_TT_FLAG_ZERO_ALLOC) ||
> -		(!ttm && ttm_bo->type == ttm_bo_type_device);
> +	needs_clear = !(bo->flags & XE_BO_FLAG_SKIP_CLEAR) &&
> +		((ttm && ttm->page_flags & TTM_TT_FLAG_ZERO_ALLOC)
> ||
> +		(!ttm && ttm_bo->type == ttm_bo_type_device));

It should be worth adding a note about how clearing for svm bos is
intended to work. From what I can tell, there is an option to clear on
migration from system to vram if no system pages are present?

>  
>  	if (new_mem->mem_type == XE_PL_TT) {
>  		ret = xe_tt_map_sg(ttm);
> @@ -1145,7 +1146,7 @@ static void xe_ttm_bo_destroy(struct
> ttm_buffer_object *ttm_bo)
>  		xe_drm_client_remove_bo(bo);
>  #endif
>  
> -	if (bo->vm && xe_bo_is_user(bo))
> +	if (bo->vm && (xe_bo_is_user(bo) || bo->flags &
> XE_BO_FLAG_SYSTEM_ALLOC))
>  		xe_vm_put(bo->vm);
>  
>  	mutex_lock(&xe->mem_access.vram_userfault.lock);
> @@ -1301,7 +1302,8 @@ struct xe_bo *___xe_bo_create_locked(struct
> xe_device *xe, struct xe_bo *bo,
>  	int err;
>  
>  	/* Only kernel objects should set GT */
> -	xe_assert(xe, !tile || type == ttm_bo_type_kernel);
> +	xe_assert(xe, !tile || type == ttm_bo_type_kernel ||
> +		  flags & XE_BO_FLAG_SYSTEM_ALLOC);
>  
>  	if (XE_WARN_ON(!size)) {
>  		xe_bo_free(bo);
> @@ -1493,7 +1495,7 @@ __xe_bo_create_locked(struct xe_device *xe,
>  	 * by having all the vm's bo refereferences released at vm
> close
>  	 * time.
>  	 */
> -	if (vm && xe_bo_is_user(bo))
> +	if (vm && (xe_bo_is_user(bo) || bo->flags &
> XE_BO_FLAG_SYSTEM_ALLOC))
>  		xe_vm_get(vm);
>  	bo->vm = vm;
>  
> @@ -2333,7 +2335,8 @@ bool xe_bo_needs_ccs_pages(struct xe_bo *bo)
>  	 * can't be used since there's no CCS storage associated
> with
>  	 * non-VRAM addresses.
>  	 */
> -	if (IS_DGFX(xe) && (bo->flags & XE_BO_FLAG_SYSTEM))
> +	if (IS_DGFX(xe) && ((bo->flags & XE_BO_FLAG_SYSTEM) ||
> +	    (bo->flags & XE_BO_FLAG_SYSTEM_ALLOC)))
>  		return false;

Can we support CCS with system allocator? Perhaps add a TODO comment if
so. I figure it should be possible if we resolve on migration to
system, which we do on BMG.


Thanks,
Thomas


>  
>  	return true;
> diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
> index 7fa44a0138b0..caf0459d16ad 100644
> --- a/drivers/gpu/drm/xe/xe_bo.h
> +++ b/drivers/gpu/drm/xe/xe_bo.h
> @@ -39,6 +39,8 @@
>  #define XE_BO_FLAG_NEEDS_64K		BIT(15)
>  #define XE_BO_FLAG_NEEDS_2M		BIT(16)
>  #define XE_BO_FLAG_GGTT_INVALIDATE	BIT(17)
> +#define XE_BO_FLAG_SYSTEM_ALLOC		BIT(18)
> +#define XE_BO_FLAG_SKIP_CLEAR		BIT(19)
>  /* this one is trigger internally only */
>  #define XE_BO_FLAG_INTERNAL_TEST	BIT(30)
>  #define XE_BO_FLAG_INTERNAL_64K		BIT(31)