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

[Alyssa Ross <hi@alyssa.is>]

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Dmitry Osipenko <dmitry.osipenko@collabora.com> writes:

> 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@redhat.com>
>> 
>> 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.

I sent
https://chromium-review.googlesource.com/c/crosvm/crosvm/+/8064741 last
week but still waiting to hear anything.  Do you have any insight into
whether it's still used / being pursued?

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