On Fri, 15 Jun 2018 15:31:43 +0300 "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > 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" <mst@xxxxxxxxxx> 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. Might be another reason to have this controlled by management software; being able to find out easily why a device is not visible to the guest seems to be a useful thing. Anyway, let's defer this discussion until it is clear how we actually want to handle the whole setup. > > > Settable may be useful if we > > find another use case for hiding realized devices. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
