On Tue, 16 Aug 2016 13:30:06 -0700 Neo Jia <c...@nvidia.com> wrote: > On Mon, Aug 15, 2016 at 04:47:41PM -0600, Alex Williamson wrote: > > On Mon, 15 Aug 2016 12:59:08 -0700 > > Neo Jia <c...@nvidia.com> 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. Also note that the semantics change when we move to per device control. It would be redundant to 'echo $UUID' into a start file which only controls a single device. So that means we probably just want an 'echo 1'. But if we can 'echo 1' then we can also 'echo 0', so we can reduce this to a single sysfs file. Sysfs already has a common interface for starting and stopping devices, the "online" file. So I think we should probably move in that direction. Additionally, an "online" file should support a _show() function, so if we have an Intel vGPU that perhaps does not need start/stop support, online could report "1" after create to show that it's already online, possibly even generate an error trying to change the online state. Thanks, Alex
