Re: [PATCH 4/5] vfio/type1: Flush CPU caches on DMA pages in non-coherent domains

[Yan Zhao]

On Tue, May 21, 2024 at 01:34:00PM -0300, Jason Gunthorpe wrote:
> On Tue, May 21, 2024 at 10:21:23AM -0600, Alex Williamson wrote:
> 
> > > Intel GPU weirdness should not leak into making other devices
> > > insecure/slow. If necessary Intel GPU only should get some variant
> > > override to keep no snoop working.
> > > 
> > > It would make alot of good sense if VFIO made the default to disable
> > > no-snoop via the config space.
> > 
> > We can certainly virtualize the config space no-snoop enable bit, but
> > I'm not sure what it actually accomplishes.  We'd then be relying on
> > the device to honor the bit and not have any backdoors to twiddle the
> > bit otherwise (where we know that GPUs often have multiple paths to get
> > to config space).
> 
> I'm OK with this. If devices are insecure then they need quirks in
> vfio to disclose their problems, we shouldn't punish everyone who
> followed the spec because of some bad actors.
Does that mean a malicous device that does not honor the bit could read
uninitialized host data?