Re: [PATCH v5 3/4] failover: fix unplug pending detection

[Michael S. Tsirkin]

On Wed, Dec 08, 2021 at 08:50:34AM +0100, Thomas Huth wrote:
> On 08/12/2021 08.36, Michael S. Tsirkin wrote:
> > On Fri, Nov 19, 2021 at 10:07:17AM +0100, Laurent Vivier wrote:
> > > Failover needs to detect the end of the PCI unplug to start migration
> > > after the VFIO card has been unplugged.
> > > 
> > > To do that, a flag is set in pcie_cap_slot_unplug_request_cb() and reset 
> > > in
> > > pcie_unplug_device().
> > > 
> > > But since
> > >      17858a169508 ("hw/acpi/ich9: Set ACPI PCI hot-plug as default on 
> > > Q35")
> > > we have switched to ACPI unplug and these functions are not called anymore
> > > and the flag not set. So failover migration is not able to detect if card
> > > is really unplugged and acts as it's done as soon as it's started. So it
> > > doesn't wait the end of the unplug to start the migration. We don't see 
> > > any
> > > problem when we test that because ACPI unplug is faster than PCIe native
> > > hotplug and when the migration really starts the unplug operation is
> > > already done.
> > > 
> > > See c000a9bd06ea ("pci: mark device having guest unplug request pending")
> > >      a99c4da9fc2a ("pci: mark devices partially unplugged")
> > > 
> > > Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> > > Reviewed-by: Ani Sinha <ani@anisinha.ca>
> > 
> > Hmm.  I think this one may be needed for this release actually.
> > Isolate from testing changes and repost?
> 
> You merged it already here:
> 
>  https://gitlab.com/qemu-project/qemu/-/commit/9323f892b39d133eb6

Oh, good. Forgot to drop the tag.

> so we should be fine :-)
> 
>  Thomas