drm/amdgpu: increase the reserved VM size to 2MB

Ideally this should be a multiple of the VM block size.
2MB should at least fit for Vega/Navi.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Madhav Chauhan <madhav.chauhan@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -115,8 +115,8 @@ struct amdgpu_bo_list_entry;
 #define AMDGPU_MMHUB_0				1
 #define AMDGPU_MMHUB_1				2
 
-/* hardcode that limit for now */
-#define AMDGPU_VA_RESERVED_SIZE			(1ULL << 20)
+/* Reserve 2MB at top/bottom of address space for kernel use */
+#define AMDGPU_VA_RESERVED_SIZE			(2ULL << 20)
 
 /* max vmids dedicated for process */
 #define AMDGPU_VM_MAX_RESERVED_VMID	1