Re: [PATCH 10/26] drm/xe: Add sa/guc_buf_cache sync interface

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

On 10/11/2025 9:38 PM, Michał Winiarski wrote:
> In upcoming changes the cached buffers are going to be used to read data
> produced by the GuC. Add a counterpart to flush, which synchronizes the
> CPU-side of suballocation with the GPU data and propagate the interface
> to GuC Buffer Cache.
> 
> Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_guc_buf.c |  9 +++++++++
>  drivers/gpu/drm/xe/xe_guc_buf.h |  1 +
>  drivers/gpu/drm/xe/xe_sa.c      | 21 +++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_sa.h      |  1 +
>  4 files changed, 32 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_buf.c b/drivers/gpu/drm/xe/xe_guc_buf.c
> index 502ca3a4ee606..1be26145f0b98 100644
> --- a/drivers/gpu/drm/xe/xe_guc_buf.c
> +++ b/drivers/gpu/drm/xe/xe_guc_buf.c
> @@ -127,6 +127,15 @@ u64 xe_guc_buf_flush(const struct xe_guc_buf buf)
>  	return xe_sa_bo_gpu_addr(buf.sa);
>  }
>  
> +/**
> + * xe_guc_buf_sync() - Copy the data from the GPU memory to the sub-allocation.
> + * @buf: the &xe_guc_buf to sync

for convenience, can we return the buf CPU pointer here?

something that I already had in my initial impl [1]

[1] https://patchwork.freedesktop.org/patch/619024/?series=139801&rev=1


> + */
> +void xe_guc_buf_sync(const struct xe_guc_buf buf)
> +{
> +	xe_sa_bo_sync(buf.sa);
> +}
> +
>  /**
>   * xe_guc_buf_cpu_ptr() - Obtain a CPU pointer to the sub-allocation.
>   * @buf: the &xe_guc_buf to query
> diff --git a/drivers/gpu/drm/xe/xe_guc_buf.h b/drivers/gpu/drm/xe/xe_guc_buf.h
> index 0d67604d96bdd..fe6b5ffe0d6eb 100644
> --- a/drivers/gpu/drm/xe/xe_guc_buf.h
> +++ b/drivers/gpu/drm/xe/xe_guc_buf.h
> @@ -31,6 +31,7 @@ static inline bool xe_guc_buf_is_valid(const struct xe_guc_buf buf)
>  
>  void *xe_guc_buf_cpu_ptr(const struct xe_guc_buf buf);
>  u64 xe_guc_buf_flush(const struct xe_guc_buf buf);
> +void xe_guc_buf_sync(const struct xe_guc_buf buf);
>  u64 xe_guc_buf_gpu_addr(const struct xe_guc_buf buf);
>  u64 xe_guc_cache_gpu_addr_from_ptr(struct xe_guc_buf_cache *cache, const void *ptr, u32 size);
>  
> diff --git a/drivers/gpu/drm/xe/xe_sa.c b/drivers/gpu/drm/xe/xe_sa.c
> index fedd017d6dd36..2115789c2bfb7 100644
> --- a/drivers/gpu/drm/xe/xe_sa.c
> +++ b/drivers/gpu/drm/xe/xe_sa.c
> @@ -110,6 +110,10 @@ struct drm_suballoc *__xe_sa_bo_new(struct xe_sa_manager *sa_manager, u32 size,
>  	return drm_suballoc_new(&sa_manager->base, size, gfp, true, 0);
>  }
>  
> +/**
> + * xe_sa_bo_flush_write() - Copy the data from the sub-allocation to the GPU memory.
> + * @sa_bo: the &drm_suballoc to flush
> + */
>  void xe_sa_bo_flush_write(struct drm_suballoc *sa_bo)
>  {
>  	struct xe_sa_manager *sa_manager = to_xe_sa_manager(sa_bo->manager);
> @@ -123,6 +127,23 @@ void xe_sa_bo_flush_write(struct drm_suballoc *sa_bo)
>  			 drm_suballoc_size(sa_bo));
>  }
>  
> +/**
> + * xe_sa_bo_sync() - Copy the data from GPU memory to the sub-allocation.
> + * @sa_bo: the &drm_suballoc to sync
> + */
> +void xe_sa_bo_sync(struct drm_suballoc *sa_bo)
> +{
> +	struct xe_sa_manager *sa_manager = to_xe_sa_manager(sa_bo->manager);
> +	struct xe_device *xe = tile_to_xe(sa_manager->bo->tile);
> +
> +	if (!sa_manager->bo->vmap.is_iomem)
> +		return;
> +
> +	xe_map_memcpy_from(xe, xe_sa_bo_cpu_addr(sa_bo), &sa_manager->bo->vmap,
> +			   drm_suballoc_soffset(sa_bo),
> +			   drm_suballoc_size(sa_bo));
> +}
> +
>  void xe_sa_bo_free(struct drm_suballoc *sa_bo,
>  		   struct dma_fence *fence)
>  {
> diff --git a/drivers/gpu/drm/xe/xe_sa.h b/drivers/gpu/drm/xe/xe_sa.h
> index 99dbf0eea5402..28fd8bb6450c2 100644
> --- a/drivers/gpu/drm/xe/xe_sa.h
> +++ b/drivers/gpu/drm/xe/xe_sa.h
> @@ -37,6 +37,7 @@ static inline struct drm_suballoc *xe_sa_bo_new(struct xe_sa_manager *sa_manager
>  }
>  
>  void xe_sa_bo_flush_write(struct drm_suballoc *sa_bo);
> +void xe_sa_bo_sync(struct drm_suballoc *sa_bo);
>  void xe_sa_bo_free(struct drm_suballoc *sa_bo, struct dma_fence *fence);
>  
>  static inline struct xe_sa_manager *