Re: [virtio-comment] [PATCH v1 1/8] admin: Add theory of operation for device migration

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Oct 12, 2023 at 11:47:05AM +0000, Parav Pandit wrote:
> 
> > From: virtio-comment@lists.oasis-open.org <virtio-comment@lists.oasis-
> > open.org> On Behalf Of Michael S. Tsirkin
> > Sent: Thursday, October 12, 2023 4:48 PM
> > On Thu, Oct 12, 2023 at 10:58:14AM +0000, Parav Pandit wrote:
> > > Sure, as I explained the config register method do not work for passthrough
> > mode, and does not scale.
> > 
> > And on the flip side, to be frank not everyone has huge guests and numbers of
> > VMs and a slower memory mapped interface for small devices might make
> > sense.  What we need to do though is make this a small non-intrusive part since
> > it's not clear such embedded cases even need live migration.
> 
> I almost sure, I am misunderstanding your point.
> 
> If the VM is small who may not need a performance, may be hypervisor can just offer
> VIRTIO_NET_F_STANDBY.
> 
> I recollect we even accelerated VIRTIO_NET_F_STANDBY flow as well.

standby hack is frankly problematic in that vm can not just be
migrated at any time.