Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver

[Neo Jia]

On Mon, Aug 15, 2016 at 04:47:41PM -0600, Alex Williamson wrote:
> On Mon, 15 Aug 2016 12:59:08 -0700
> Neo Jia <address@hidden> wrote:
> 
> > > > >
> > > > > I'm not sure a comma separated list makes sense here, for both
> > > > > simplicity in the kernel and more fine grained error reporting, we
> > > > > probably want to start/stop them individually.  Actually, why is it
> > > > > that we can't use the mediated device being opened and released to
> > > > > automatically signal to the backend vendor driver to commit and 
> > > > > release
> > > > > resources? I don't fully understand why userspace needs this 
> > > > > interface.  
> > > 
> 
> That doesn't give an individual user the ability to stop and start
> their devices though, because in order for a user to have write
> permissions there, they get permission to DoS other users by pumping
> arbitrary UUIDs into those files.  By placing start/stop per mdev, we
> have mdev level granularity of granting start/stop privileges.  Really
> though, do we want QEMU fumbling around through sysfs or do we want an
> interface through the vfio API to perform start/stop?  Thanks,

Hi Alex,

I think those two suggests make sense, so we will move the "start/stop"
under mdev sysfs. 

This will be incorporated in our next v7 patch and by doing that, it will make
the locking scheme easier.

Thanks,
Neo

> 
> Alex