Re: [PATCH v3] failover: fix unplug pending detection

[Ani Sinha]

On Tue, 5 Oct 2021, Laurent Vivier wrote:

> On 05/10/2021 17:14, Michael S. Tsirkin wrote:
> > On Fri, Oct 01, 2021 at 10:25:02AM +0200, 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>
> >
> > Laurent, are you thinking of addressing Gerd's comment?
>
> No, because as said by Ani, it's not the scope of this patch. The patch only
> aligns ACPI to PCIe Native to be able to manage failover.
>
> The problem reported by Gerd and Daniel has been introduced by another patch,
> globally.
>

but I thought Julia's fix commit cce8944cc9efab47d4bf29cfffb3470371c3541b
addressed this for native pcie and since it is at a high enough level, it
should catch the acpi hotplug path equally as well.