Re: [PATCH 2/3] drm/xe: Update xe_migrate_vram to support compression

[Matthew Auld <matthew.auld@intel.com>]

On 14/07/2025 18:33, Matthew Brost wrote:
> While SVM does not currently support compression, other users of
> xe_migrate_vram (e.g., devcoredump) expect the data to be read back
> uncompressed. Update xe_migrate_vram to support compressed data.
> 
> Cc: stable@vger.kernel.org
> Fixes: 9c44fd5f6e8a ("drm/xe: Add migrate layer functions for SVM support")
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_migrate.c | 31 ++++++++++++++++++++++++-------
>   1 file changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
> index ba1cff2e4cda..936daa2b363d 100644
> --- a/drivers/gpu/drm/xe/xe_migrate.c
> +++ b/drivers/gpu/drm/xe/xe_migrate.c
> @@ -1613,7 +1613,8 @@ static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
>   					 unsigned long len,
>   					 unsigned long sram_offset,
>   					 dma_addr_t *sram_addr, u64 vram_addr,
> -					 const enum xe_migrate_copy_dir dir)
> +					 const enum xe_migrate_copy_dir dir,
> +					 bool needs_ccs_emit)
>   {
>   	struct xe_gt *gt = m->tile->primary_gt;
>   	struct xe_device *xe = gt_to_xe(gt);
> @@ -1623,10 +1624,12 @@ static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
>   	u64 src_L0_ofs, dst_L0_ofs;
>   	struct xe_sched_job *job;
>   	struct xe_bb *bb;
> -	u32 update_idx, pt_slot = 0;
> +	u32 update_idx, pt_slot = 0, flush_flags = 0;
>   	unsigned long npages = DIV_ROUND_UP(len + sram_offset, PAGE_SIZE);
>   	unsigned int pitch = len >= PAGE_SIZE && !(len & ~PAGE_MASK) ?
>   		PAGE_SIZE : 4;
> +	bool use_comp_pat = xe_device_has_flat_ccs(xe) &&
> +		GRAPHICS_VER(xe) >= 20 && dir == XE_MIGRATE_COPY_TO_SRAM;
>   	int err;
>   
>   	if (drm_WARN_ON(&xe->drm, (len & XE_CACHELINE_MASK) ||
> @@ -1637,6 +1640,8 @@ static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
>   
>   	batch_size += pte_update_cmd_size(len);
>   	batch_size += EMIT_COPY_DW;
> +	if (needs_ccs_emit)
> +		batch_size += EMIT_COPY_CCS_DW;
>   
>   	bb = xe_bb_new(gt, batch_size, use_usm_batch);
>   	if (IS_ERR(bb)) {
> @@ -1652,7 +1657,7 @@ static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
>   		dst_L0_ofs = xe_migrate_vram_ofs(xe, vram_addr, false);
>   
>   	} else {
> -		src_L0_ofs = xe_migrate_vram_ofs(xe, vram_addr, false);
> +		src_L0_ofs = xe_migrate_vram_ofs(xe, vram_addr, use_comp_pat);
>   		dst_L0_ofs = xe_migrate_vm_addr(pt_slot, 0) + sram_offset;
>   	}
>   
> @@ -1661,6 +1666,17 @@ static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
>   
>   	emit_copy(gt, bb, src_L0_ofs, dst_L0_ofs, len, pitch);
>   
> +	if (needs_ccs_emit) {
> +		if (dir == XE_MIGRATE_COPY_TO_VRAM)
> +			flush_flags = xe_migrate_ccs_copy(m, bb, src_L0_ofs,
> +							  false, dst_L0_ofs,
> +							  true, len, 0, true);
> +		else
> +			flush_flags = xe_migrate_ccs_copy(m, bb, src_L0_ofs,
> +							  true, dst_L0_ofs,
> +							  false, len, 0, true);
> +	}

I think we can drop this and anything related to needs_ccs_emit.  In 
theory we should only need the use_comp_pat change. IIUC this path is 
VRAM only, and only xe2+ can be decompressed in the KMD (dg2 is no-go), 
and for that we don't manage the raw CCS state.

> +
>   	job = xe_bb_create_migration_job(m->q, bb,
>   					 xe_migrate_batch_base(m, use_usm_batch),
>   					 update_idx);
> @@ -1669,7 +1685,7 @@ static struct dma_fence *xe_migrate_vram(struct xe_migrate *m,
>   		goto err;
>   	}
>   
> -	xe_sched_job_add_migrate_flush(job, 0);
> +	xe_sched_job_add_migrate_flush(job, flush_flags);
>   
>   	mutex_lock(&m->job_mutex);
>   	xe_sched_job_arm(job);
> @@ -1708,7 +1724,7 @@ struct dma_fence *xe_migrate_to_vram(struct xe_migrate *m,
>   				     u64 dst_addr)
>   {
>   	return xe_migrate_vram(m, npages * PAGE_SIZE, 0, src_addr, dst_addr,
> -			       XE_MIGRATE_COPY_TO_VRAM);
> +			       XE_MIGRATE_COPY_TO_VRAM, false);
>   }
>   
>   /**
> @@ -1729,7 +1745,7 @@ struct dma_fence *xe_migrate_from_vram(struct xe_migrate *m,
>   				       dma_addr_t *dst_addr)
>   {
>   	return xe_migrate_vram(m, npages * PAGE_SIZE, 0, dst_addr, src_addr,
> -			       XE_MIGRATE_COPY_TO_SRAM);
> +			       XE_MIGRATE_COPY_TO_SRAM, false);
>   }
>   
>   static void xe_migrate_dma_unmap(struct xe_device *xe, dma_addr_t *dma_addr,
> @@ -1890,7 +1906,8 @@ int xe_migrate_access_memory(struct xe_migrate *m, struct xe_bo *bo,
>   					  dma_addr + current_page,
>   					  vram_addr, write ?
>   					  XE_MIGRATE_COPY_TO_VRAM :
> -					  XE_MIGRATE_COPY_TO_SRAM);
> +					  XE_MIGRATE_COPY_TO_SRAM,
> +					  xe_bo_needs_ccs_pages(bo));
>   		if (IS_ERR(__fence)) {
>   			if (fence)
>   				dma_fence_wait(fence, false);