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From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Laurent Vivier <lvivier@redhat.com>,
	Juan Quintela <quintela@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	qemu-devel@nongnu.org, Ani Sinha <ani@anisinha.ca>,
	Igor Mammedov <imammedo@redhat.com>,
	Jens Freimann <jfreimann@redhat.com>
Subject: Re: [PATCH v3] failover: fix unplug pending detection
Date: Fri, 1 Oct 2021 11:48:55 +0100	[thread overview]
Message-ID: <YVbnl7hcvNLMYj/e@redhat.com> (raw)
In-Reply-To: <20211001104514.46bhlpenx4rz2qnm@sirius.home.kraxel.org>

On Fri, Oct 01, 2021 at 12:45:14PM +0200, Gerd Hoffmann 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().
> 
> > +    /*
> > +     * 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).

That's important because OpenStack will definitely trigger
multiple device_del commands in a row if they don't get a
success from an initial one.

Regards,
Daniel
-- 
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  reply	other threads:[~2021-10-01 10:50 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-01  8:25 [PATCH v3] failover: fix unplug pending detection Laurent Vivier
2021-10-01 10:45 ` Gerd Hoffmann
2021-10-01 10:48   ` Daniel P. Berrangé [this message]
2021-10-01 11:01   ` Laurent Vivier
2021-10-01 12:49     ` Gerd Hoffmann
2021-10-01 13:17       ` Ani Sinha
2021-10-01 15:19       ` Ani Sinha
2021-10-05 15:14 ` Michael S. Tsirkin
2021-10-05 16:01   ` Laurent Vivier
2021-10-06  5:53     ` Ani Sinha
2021-10-18  7:19 ` Laurent Vivier
2021-10-18  8:27   ` Michael S. Tsirkin
2021-11-18  9:15     ` Laurent Vivier
2021-11-18 10:04       ` Ani Sinha

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