Re: [PATCH v4] drm/virtio: Add option to disable KMS support

[Dmitry Osipenko]

On 2/28/23 18:54, Rob Clark wrote:
> From: Rob Clark <robdclark@xxxxxxxxxxxx>
> 
> Add a build option to disable modesetting support.  This is useful in
> cases where the guest only needs to use the GPU in a headless mode, or
> (such as in the CrOS usage) window surfaces are proxied to a host
> compositor.
> 
> As the modesetting ioctls are a big surface area for potential security
> bugs to be found (it's happened in the past, we should assume it will
> again in the future), it makes sense to have a build option to disable
> those ioctls in cases where they serve no legitimate purpose.
> 
> v2: Use more if (IS_ENABLED(...))
> v3: Also permit the host to advertise no scanouts
> v4: Spiff out commit msg
> 
> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> Reviewed-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---

Gerd, to give you some context on the v4.. we've chatted a bit more on
the #dri-devel and concluded that config option is the most robust way
of having KMS disabled from a security stand point. We would also want
to have a per-driver option (and not global) because there are scenarios
of using passthrough GPU + virtio-gpu in a guest, hence we would only
want to toggle KMS for a particular driver.

-- 
Best regards,
Dmitry