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Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver
From: |
Alex Williamson |
Subject: |
Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver |
Date: |
Tue, 16 Aug 2016 14:51:03 -0600 |
On Tue, 16 Aug 2016 13:30:06 -0700
Neo Jia <address@hidden> 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 <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. 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
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, (continued)
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Alex Williamson, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Alex Williamson, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Tian, Kevin, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Alex Williamson, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Tian, Kevin, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/16
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver,
Alex Williamson <=
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/16
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Tian, Kevin, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Tian, Kevin, 2016/08/15
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/16
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Tian, Kevin, 2016/08/16
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/16
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Tian, Kevin, 2016/08/16
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Neo Jia, 2016/08/16
- Re: [Qemu-devel] [PATCH v6 1/4] vfio: Mediated device Core driver, Alex Williamson, 2016/08/16