[PATCH 2/3] drm/amdgpu: reserve at least 4MB of VRAM for page tables

[Christian König]

This hopefully helps reduce the contention for page tables.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h       | 3 +++
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 9 +++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index 2eda3a8c330d..3352a87b822e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -99,6 +99,9 @@ struct amdgpu_bo_list_entry;
 #define AMDGPU_VM_FAULT_STOP_FIRST	1
 #define AMDGPU_VM_FAULT_STOP_ALWAYS	2
 
+/* Reserve 4MB VRAM for page tables */
+#define AMDGPU_VM_RESERVED_VRAM		(4ULL << 20)
+
 /* max number of VMHUB */
 #define AMDGPU_MAX_VMHUBS			3
 #define AMDGPU_GFXHUB_0				0
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index 1150e34bc28f..59440f71d304 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -24,6 +24,7 @@
 
 #include <drm/drmP.h>
 #include "amdgpu.h"
+#include "amdgpu_vm.h"
 
 struct amdgpu_vram_mgr {
 	struct drm_mm mm;
@@ -276,7 +277,7 @@ static int amdgpu_vram_mgr_new(struct ttm_mem_type_manager *man,
 	struct drm_mm_node *nodes;
 	enum drm_mm_insert_mode mode;
 	unsigned long lpfn, num_nodes, pages_per_node, pages_left;
-	uint64_t vis_usage = 0, mem_bytes;
+	uint64_t vis_usage = 0, mem_bytes, max_bytes;
 	unsigned i;
 	int r;
 
@@ -284,9 +285,13 @@ static int amdgpu_vram_mgr_new(struct ttm_mem_type_manager *man,
 	if (!lpfn)
 		lpfn = man->size;
 
+	max_bytes = adev->gmc.mc_vram_size;
+	if (tbo->type != ttm_bo_type_kernel)
+		max_bytes -= AMDGPU_VM_RESERVED_VRAM;
+
 	/* bail out quickly if there's likely not enough VRAM for this BO */
 	mem_bytes = (u64)mem->num_pages << PAGE_SHIFT;
-	if (atomic64_add_return(mem_bytes, &mgr->usage) > adev->gmc.mc_vram_size) {
+	if (atomic64_add_return(mem_bytes, &mgr->usage) > max_bytes) {
 		atomic64_sub(mem_bytes, &mgr->usage);
 		mem->mm_node = NULL;
 		return 0;
-- 
2.17.1