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

[Gerd Hoffmann]

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().

> +    /*
> +     * pending_deleted_event is used by virtio-net failover to detect the
> +     * end of the unplug operation, the flag is set to false in
> +     * acpi_pcihp_eject_slot() when the operation is completed.
> +     */
> +    pdev->qdev.pending_deleted_event = true;

This has the side effect of blocking a second 'device_del' command.

So, in case the first time didn't work (for example due to the guest not
listening because grub just doesn't do that), you can try a second time
once the linux kernel is up'n'running.

I suspect this patch will break that (didn't actually test though).


While being at it I'll throw in a link to a bunch of slightly related
pcie hotplug patches:
   https://gitlab.com/kraxel/qemu/-/commits/sirius/pcie-hotplug

I'll be offline next week, so not posting that series for discussion
yet, will probably do that when I'm back, but you might want have a
look nevertheless.

take care,
  Gerd