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

[Thomas Huth <thuth@redhat.com>]

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

so we should be fine :-)

  Thomas