2 files changed, 82 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 5c3f24069f2a..953d68b26f0b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -50,6 +50,7 @@
 #include <drm/ttm/ttm_range_manager.h>
 
 #include <drm/amdgpu_drm.h>
+#include <drm/drm_drv.h>
 
 #include "amdgpu.h"
 #include "amdgpu_object.h"
@@ -1433,6 +1434,70 @@ static void amdgpu_ttm_vram_mm_access(struct amdgpu_device *adev, loff_t pos,
 	}
 }
 
+static int amdgpu_ttm_access_memory_sdma(struct ttm_buffer_object *bo,
+					unsigned long offset, void *buf, int len, int write)
+{
+	struct amdgpu_bo *abo = ttm_to_amdgpu_bo(bo);
+	struct amdgpu_device *adev = amdgpu_ttm_adev(abo->tbo.bdev);
+	struct amdgpu_job *job;
+	struct dma_fence *fence;
+	uint64_t src_addr, dst_addr;
+	unsigned int num_dw;
+	int r, idx;
+
+	if (len != PAGE_SIZE)
+		return -EINVAL;
+
+	if (!adev->mman.sdma_access_ptr)
+		return -EACCES;
+
+	r = drm_dev_enter(adev_to_drm(adev), &idx);
+	if (r)
+		return r;
+
+	if (write)
+		memcpy(adev->mman.sdma_access_ptr, buf, len);
+
+	num_dw = ALIGN(adev->mman.buffer_funcs->copy_num_dw, 8);
+	r = amdgpu_job_alloc_with_ib(adev, num_dw * 4, AMDGPU_IB_POOL_DELAYED, &job);
+	if (r)
+		goto out;
+
+	src_addr = write ? amdgpu_bo_gpu_offset(adev->mman.sdma_access_bo) :
+			amdgpu_bo_gpu_offset(abo);
+	dst_addr = write ? amdgpu_bo_gpu_offset(abo) :
+			amdgpu_bo_gpu_offset(adev->mman.sdma_access_bo);
+	amdgpu_emit_copy_buffer(adev, &job->ibs[0], src_addr, dst_addr, PAGE_SIZE, false);
+
+	amdgpu_ring_pad_ib(adev->mman.buffer_funcs_ring, &job->ibs[0]);
+	WARN_ON(job->ibs[0].length_dw > num_dw);
+
+	r = amdgpu_job_submit(job, &adev->mman.entity, AMDGPU_FENCE_OWNER_UNDEFINED, &fence);
+	if (r) {
+		amdgpu_job_free(job);
+		goto out;
+	}
+
+	if (!dma_fence_wait_timeout(fence, false, adev->sdma_timeout))
+		r = -ETIMEDOUT;
+	dma_fence_put(fence);
+
+	if (!(r || write))
+		memcpy(buf, adev->mman.sdma_access_ptr, len);
+out:
+	drm_dev_exit(idx);
+	return r;
+}
+
+static inline bool amdgpu_ttm_allow_post_mortem_debug(struct amdgpu_device *adev)
+{
+	return amdgpu_gpu_recovery == 0 ||
+		adev->gfx_timeout == MAX_SCHEDULE_TIMEOUT ||
+		adev->compute_timeout == MAX_SCHEDULE_TIMEOUT ||
+		adev->sdma_timeout == MAX_SCHEDULE_TIMEOUT ||
+		adev->video_timeout == MAX_SCHEDULE_TIMEOUT;
+}
+
 /**
  * amdgpu_ttm_access_memory - Read or Write memory that backs a buffer object.
  *
@@ -1457,6 +1522,10 @@ static int amdgpu_ttm_access_memory(struct ttm_buffer_object *bo,
 	if (bo->resource->mem_type != TTM_PL_VRAM)
 		return -EIO;
 
+	if (!amdgpu_ttm_allow_post_mortem_debug(adev) &&
+			!amdgpu_ttm_access_memory_sdma(bo, offset, buf, len, write))
+		return len;
+
 	amdgpu_res_first(bo->resource, offset, len, &cursor);
 	while (cursor.remaining) {
 		size_t count, size = cursor.size;
@@ -1797,6 +1866,12 @@ int amdgpu_ttm_init(struct amdgpu_device *adev)
 		return r;
 	}
 
+	if (amdgpu_bo_create_kernel(adev, PAGE_SIZE, PAGE_SIZE,
+				AMDGPU_GEM_DOMAIN_GTT,
+				&adev->mman.sdma_access_bo, NULL,
+				adev->mman.sdma_access_ptr))
+		DRM_WARN("Debug VRAM access will use slowpath MM access\n");
+
 	return 0;
 }
 
@@ -1837,6 +1912,9 @@ void amdgpu_ttm_fini(struct amdgpu_device *adev)
 	ttm_range_man_fini(&adev->mman.bdev, AMDGPU_PL_OA);
 	ttm_device_fini(&adev->mman.bdev);
 	adev->mman.initialized = false;
+	if (adev->mman.sdma_access_ptr)
+		amdgpu_bo_free_kernel(&adev->mman.sdma_access_bo, NULL,
+					&adev->mman.sdma_access_ptr);
 	DRM_INFO("amdgpu: ttm finalized\n");
 }
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
index f8f48be16d80..f06fd19b4895 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
@@ -98,6 +98,10 @@ struct amdgpu_mman {
 	u64		fw_vram_usage_size;
 	struct amdgpu_bo	*fw_vram_usage_reserved_bo;
 	void		*fw_vram_usage_va;
+
+	/* PAGE_SIZE'd BO for process memory r/w over SDMA. */
+	struct amdgpu_bo	*sdma_access_bo;
+	void			*sdma_access_ptr;
 };
 
 struct amdgpu_copy_mem {