diff options
| author | Harkirat Gill <harkirat.gill@amd.com> | 2026-07-27 14:37:56 -0400 |
|---|---|---|
| committer | Alex Deucher <alexander.deucher@amd.com> | 2026-07-28 20:01:16 -0400 |
| commit | 5e70f6804b4d6256058c360b10e044ee04ea4a4e (patch) | |
| tree | 46b36c247d6ea88a9258c0ad1ff0bcac194a133d | |
| parent | 1849a64165ccc23d3e5fc22b8be19227c21c1871 (diff) | |
drm/amdgpu: cap GTT size to physical RAM on APUs
On APUs, the GTT pool is backed by system RAM, but its size is not bound
to the non-carveout memory that actually backs it. A user can end up
with GTT + VRAM exceeding total physical memory through the following
sequence:
- Have a large non-carveout memory space (~128GB) and accordingly set a
large GTT (~100GB) via the ttm module parameter.
- Lower the non-carveout memory space in BIOS by increasing the UMA
Frame Buffer Size (VRAM) to 64GB.
- The previously set GTT value (~100GB) persists, even though the new
non-carveout space (64GB) can no longer back it.
This leads to a case where kernel reports GTT (100GB) + VRAM (64GB)
despite the sum being greater than total physical memory (128GB).
Cap the GTT size to totalram_pages() on APUs. totalram_pages() already
excludes the VRAM carveout, so the resulting GTT can never exceed the
system RAM that actually backs it.
Signed-off-by: Harkirat Gill <harkirat.gill@amd.com>
Reviewed-by: David Francis <David.Francis@amd.com>
Assisted-by: Claude:claude-opus-4
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 5dafdd649280c7dc6c22c8f877da3f54fcc441e1)
Cc: stable@vger.kernel.org
| -rw-r--r-- | drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c index eb8bbfc7e6d9..5fc91f45db5b 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c @@ -2173,6 +2173,18 @@ int amdgpu_ttm_init(struct amdgpu_device *adev) gtt_size = configured_size; } + /* Cap GTT so that it does not exceed total physical RAM. */ + if (adev->flags & AMD_IS_APU) { + u64 phys_ram = (u64)totalram_pages() << PAGE_SHIFT; + + if (gtt_size > phys_ram) { + gtt_size = phys_ram; + dev_info(adev->dev, + "Capping GTT to %uM to not exceed available system memory\n", + (unsigned int)(gtt_size / (1024 * 1024))); + } + } + /* Initialize GTT memory pool */ r = amdgpu_gtt_mgr_init(adev, gtt_size); if (r) { |