[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.koe...@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

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