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

[Laurent Vivier <lvivier@redhat.com>]

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.

Except if you think it's really required I will not send a new version.

Thanks,
Laurent