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Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_S
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net |
Date: |
Fri, 15 Jun 2018 15:31:43 +0300 |
On Fri, Jun 15, 2018 at 11:32:42AM +0200, Cornelia Huck wrote:
> On Fri, 15 Jun 2018 05:34:24 +0300
> "Michael S. Tsirkin" <address@hidden> wrote:
>
> > On Thu, Jun 14, 2018 at 12:02:31PM +0200, Cornelia Huck wrote:
>
> > > > > I am not all that familiar with how Qemu manages network devices. If
> > > > > we can
> > > > > do all the
> > > > > required management of the primary/standby devices within Qemu, that
> > > > > is
> > > > > definitely a better
> > > > > approach without upper layer involvement.
> > > >
> > > > Right. I would imagine in the extreme case the upper layer doesn't
> > > > have to be involved at all if QEMU manages all hot plug/unplug logic.
> > > > The management tool can supply passthrough device and virtio with the
> > > > same group UUID, QEMU auto-manages the presence of the primary, and
> > > > hot plug the device as needed before or after the migration.
> > >
> > > I do not really see how you can manage that kind of stuff in QEMU only.
> >
> > So right now failover is limited to pci passthrough devices only.
> > The idea is to realize the vfio device but not expose it
> > to guest. Have a separate command to expose it to guest.
> > Hotunplug would also hide it from guest but not unrealize it.
>
> So, this would not be real hot(un)plug, but 'hide it from the guest',
> right? The concept of "we have it realized in QEMU, but the guest can't
> discover and use it" should be translatable to non-pci as well (at
> least for ccw).
>
> >
> > This will help ensure that e.g. on migration failure we can
> > re-expose the device without risk of running out of resources.
>
> Makes sense.
>
> Should that 'hidden' state be visible/settable from outside as well
> (e.g. via a property)? I guess yes, so that management software has a
> chance to see whether a device is visible.
Might be handy for debug, but note that since QEMU manages this
state it's transient: can change at any time, so it's kind
of hard for management to rely on it.
> Settable may be useful if we
> find another use case for hiding realized devices.
- Re: [Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, (continued)
- Re: [Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Samudrala, Sridhar, 2018/06/12
- Re: [Qemu-devel] [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Michael S. Tsirkin, 2018/06/12
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Samudrala, Sridhar, 2018/06/12
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Siwei Liu, 2018/06/13
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Cornelia Huck, 2018/06/14
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Siwei Liu, 2018/06/14
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Cornelia Huck, 2018/06/15
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Siwei Liu, 2018/06/15
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Michael S. Tsirkin, 2018/06/14
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Cornelia Huck, 2018/06/15
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Cornelia Huck, 2018/06/18
- Re: [Qemu-devel] [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net, Michael S. Tsirkin, 2018/06/14