drm/amdgpu: Raise KFD unpinned system memory limit

Allow KFD applications to use more unpinned system memory through
HMM.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Yong Zhao <Yong.Zhao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -85,7 +85,7 @@ static bool check_if_add_bo_to_vm(struct amdgpu_vm *avm,
 }
 
 /* Set memory usage limits. Current, limits are
- *  System (TTM + userptr) memory - 3/4th System RAM
+ *  System (TTM + userptr) memory - 15/16th System RAM
  *  TTM memory - 3/8th System RAM
  */
 void amdgpu_amdkfd_gpuvm_init_mem_limits(void)
@@ -98,7 +98,7 @@ void amdgpu_amdkfd_gpuvm_init_mem_limits(void)
 	mem *= si.mem_unit;
 
 	spin_lock_init(&kfd_mem_limit.mem_limit_lock);
-	kfd_mem_limit.max_system_mem_limit = (mem >> 1) + (mem >> 2);
+	kfd_mem_limit.max_system_mem_limit = mem - (mem >> 4);
 	kfd_mem_limit.max_ttm_mem_limit = (mem >> 1) - (mem >> 3);
 	pr_debug("Kernel memory limit %lluM, TTM limit %lluM\n",
 		(kfd_mem_limit.max_system_mem_limit >> 20),