Re: [PATCH v2 2/3] drm/virtio: honor blob_alignment requirements

[Dmitry Osipenko]

On 7/1/26 14:10, Alyssa Ross wrote:
> On Tue, Apr 28, 2026 at 09:44:49PM +0200, Sergio Lopez wrote:
>> If VIRTIO_GPU_F_BLOB_ALIGNMENT has been negotiated, blob size must be
>> aligned to blob_alignment. Validate this in verify_blob() so that
>> invalid requests are rejected early.
>>
>> Signed-off-by: Sergio Lopez <slp@xxxxxxxxxx>
> 
> FYI: this change breaks crosvm, which is squatting the 5 and 6 values
> of VIRTIO_GPU_F_* with different meanings.  I've reported it as a
> crosvm bug, so hopefully it can be taken care of there.
> 
> https://issuetracker.google.com/issues/529852979
> 
>> ---
>>  drivers/gpu/drm/virtio/virtgpu_ioctl.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> index c33c057365f8..d0c4edf1eaf4 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
>> @@ -489,6 +489,11 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
>>  	params->size = rc_blob->size;
>>  	params->blob = true;
>>  	params->blob_flags = rc_blob->blob_flags;
>> +
>> +	if (vgdev->has_blob_alignment &&
>> +	    !IS_ALIGNED(params->size, vgdev->blob_alignment))
>> +		return -EINVAL;
>> +
>>  	return 0;
>>  }
>>
>> --
>> 2.53.0
>>

Thanks for the report. Indeed, crosvm will need to fix its experimental
caps. CI will likely run into this problem first once it will update
guest to 7.2+ kernel.

-- 
Best regards,
Dmitry