Re: [PATCH] drm/amdgpu: fix an underflow on non-4KB-page systems

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Am 29.03.21 um 20:08 schrieb Xi Ruoyao:
On 2021-03-29 20:04 +0200, Christian König wrote:
Am 29.03.21 um 19:53 schrieb Xℹ Ruoyao:
If the initial value of `num_entires` (calculated at line 1654) is not
an integral multiple of `AMDGPU_GPU_PAGES_IN_CPU_PAGE`, in line 1681 a
value greater than the initial value will be assigned to it.  That causes
`start > last + 1` after line 1708.  Then in the next iteration an
underflow happens at line 1654.  It causes message

      *ERROR* Couldn't update BO_VA (-12)

printed in kernel log, and GPU hanging.

Fortify the criteria of the loop to fix this issue.
NAK the value of num_entries must always be a multiple of
AMDGPU_GPU_PAGES_IN_CPU_PAGE or otherwise we corrupt the page tables.

How do you trigger that?
Simply run "OpenGL area" from gtk3-demo (which just renders a triangle with GL)
under Xorg, on MIPS64.  See the BugLink.

You need to identify the root cause of this, most likely start or last are not a multiple of AMDGPU_GPU_PAGES_IN_CPU_PAGE.

Christian.


Christian.

BugLink: https://gitlab.freedesktop.org/drm/amd/-/issues/1549
Fixes: a39f2a8d7066 ("drm/amdgpu: nuke amdgpu_vm_bo_split_mapping v2")
Reported-by: Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx>
Reported-by: Dan Horák <dan@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 2 +-
   1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index ad91c0c3c423..cee0cc9c8085 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1707,7 +1707,7 @@ static int amdgpu_vm_bo_update_mapping(struct
amdgpu_device *adev,
                 }
                 start = tmp;
-       } while (unlikely(start != last + 1));
+       } while (unlikely(start < last + 1));
        r = vm->update_funcs->commit(&params, fence);
base-commit: a5e13c6df0e41702d2b2c77c8ad41677ebb065b3

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