On Wed, Mar 01, 2023 at 03:37:24AM +0300, Dmitry Osipenko wrote: > 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. IMHO both ways options to disable the KMS bits should work the same way. With the current patch modeset_init() runs with num_scanouts == 0 but doesn't with CONFIG_KMS=n. There are also two different ways to tweak driver_features. Can we get rid of that please, for robustness reasons? I'd suggest to have a is_kms_enabled() helper function (probably best as inline so gcc can figure it is constant false for CONFIG_KMS=n and throw away unreachable code). Add "if (!is_kms_enabled()) return;" to modeset_init() and modeset_fini() instead of stubbing them out. Use the drm_device->driver_features override in both cases. Also the edid check can go away. As already mentioned this is about a device feature not a edid being present. take care, Gerd _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
