drm/amdgpu: Enable P2P dmabuf over XGMI

Access the exported P2P dmabuf over XGMI, if available.
Otherwise, fall back to the existing PCIe method.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Arunpravin <apaneers@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c

@@ -35,6 +35,7 @@
 #include "amdgpu_display.h"
 #include "amdgpu_gem.h"
 #include "amdgpu_dma_buf.h"
+#include "amdgpu_xgmi.h"
 #include <drm/amdgpu_drm.h>
 #include <linux/dma-buf.h>
 #include <linux/dma-fence-array.h>
@@ -595,3 +596,36 @@ struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
 	obj->import_attach = attach;
 	return obj;
 }
+
+/**
+ * amdgpu_dmabuf_is_xgmi_accessible - Check if xgmi available for P2P transfer
+ *
+ * @adev: amdgpu_device pointer of the importer
+ * @bo: amdgpu buffer object
+ *
+ * Returns:
+ * True if dmabuf accessible over xgmi, false otherwise.
+ */
+bool amdgpu_dmabuf_is_xgmi_accessible(struct amdgpu_device *adev,
+				      struct amdgpu_bo *bo)
+{
+	struct drm_gem_object *obj = &bo->tbo.base;
+	struct drm_gem_object *gobj;
+
+	if (obj->import_attach) {
+		struct dma_buf *dma_buf = obj->import_attach->dmabuf;
+
+		if (dma_buf->ops != &amdgpu_dmabuf_ops)
+			/* No XGMI with non AMD GPUs */
+			return false;
+
+		gobj = dma_buf->priv;
+		bo = gem_to_amdgpu_bo(gobj);
+	}
+
+	if (amdgpu_xgmi_same_hive(adev, amdgpu_ttm_adev(bo->tbo.bdev)) &&
+			(bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM))
+		return true;
+
+	return false;
+}

drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.h

@@ -29,6 +29,8 @@ struct dma_buf *amdgpu_gem_prime_export(struct drm_gem_object *gobj,
 					int flags);
 struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
 					    struct dma_buf *dma_buf);
+bool amdgpu_dmabuf_is_xgmi_accessible(struct amdgpu_device *adev,
+				      struct amdgpu_bo *bo);
 void *amdgpu_gem_prime_vmap(struct drm_gem_object *obj);
 void amdgpu_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr);
 int amdgpu_gem_prime_mmap(struct drm_gem_object *obj,

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -28,6 +28,7 @@
 #include <linux/dma-fence-array.h>
 #include <linux/interval_tree_generic.h>
 #include <linux/idr.h>
+#include <linux/dma-buf.h>
 
 #include <drm/amdgpu_drm.h>
 #include "amdgpu.h"
@@ -35,6 +36,7 @@
 #include "amdgpu_amdkfd.h"
 #include "amdgpu_gmc.h"
 #include "amdgpu_xgmi.h"
+#include "amdgpu_dma_buf.h"
 
 /**
  * DOC: GPUVM
@@ -1778,15 +1780,24 @@ int amdgpu_vm_bo_update(struct amdgpu_device *adev, struct amdgpu_bo_va *bo_va,
 		nodes = NULL;
 		resv = vm->root.base.bo->tbo.base.resv;
 	} else {
+		struct drm_gem_object *obj = &bo->tbo.base;
 		struct ttm_dma_tt *ttm;
 
+		resv = bo->tbo.base.resv;
+		if (obj->import_attach && bo_va->is_xgmi) {
+			struct dma_buf *dma_buf = obj->import_attach->dmabuf;
+			struct drm_gem_object *gobj = dma_buf->priv;
+			struct amdgpu_bo *abo = gem_to_amdgpu_bo(gobj);
+
+			if (abo->tbo.mem.mem_type == TTM_PL_VRAM)
+				bo = gem_to_amdgpu_bo(gobj);
+		}
 		mem = &bo->tbo.mem;
 		nodes = mem->mm_node;
 		if (mem->mem_type == TTM_PL_TT) {
 			ttm = container_of(bo->tbo.ttm, struct ttm_dma_tt, ttm);
 			pages_addr = ttm->dma_address;
 		}
-		resv = bo->tbo.base.resv;
 	}
 
 	if (bo) {
@@ -2132,8 +2143,10 @@ struct amdgpu_bo_va *amdgpu_vm_bo_add(struct amdgpu_device *adev,
 	INIT_LIST_HEAD(&bo_va->valids);
 	INIT_LIST_HEAD(&bo_va->invalids);
 
-	if (bo && amdgpu_xgmi_same_hive(adev, amdgpu_ttm_adev(bo->tbo.bdev)) &&
-	    (bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM)) {
+	if (!bo)
+		return bo_va;
+
+	if (amdgpu_dmabuf_is_xgmi_accessible(adev, bo)) {
 		bo_va->is_xgmi = true;
 		/* Power up XGMI if it can be potentially used */
 		amdgpu_xgmi_set_pstate(adev, AMDGPU_XGMI_PSTATE_MAX_VEGA20);