[virglrenderer-devel] coherent memory access for virgl

[Gerd Hoffmann]

On Fri, Mar 08, 2019 at 10:43:04AM +0100, Tomeu Vizoso wrote:
> On 10/11/18 1:04 PM, Gerd Hoffmann wrote:
> > 
> > > * virtio-gpu resource IDs are placed by the guest proxy in the wl_dmabuf
> > > protocol stream instead of (guest) dmabuf FDs. The proxy in the host
> > > replaces those to the corresponding (host) dmabuf FD.
> > 
> > Yes.
> 
> Hi Gerd,
> 
> how were you thinking that we would prevent a malicious guest from
> connecting to the host proxy via VSOCK and guessing virtio-gpu resource IDs?

Each virtio-gpu device (and therefore each guest) has its own resource
id namespace, so you can't guess IDs of other guests.  Guessing IDs of
other processes in the same guest is probably possible.  I think that
doesn't allow actually accessing these resources, you can only ask the
host to do something with them.

Maybe that is a good reason do make wayland proxying a virtio-gpu
extension.  That way guest userspace would not deal with virtio-gpu
resource IDs but with gbm handles, and the virtio-gpu drm driver would
translate gbm handles to resource ids before proxying buffer control
messages to the host side.

cheers,
  Gerd