From: "Michael S. Tsirkin" <mst@redhat.com>
To: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>,
"yc-core@yandex-team.ru" <yc-core@yandex-team.ru>,
"Juan Quintela" <quintela@redhat.com>,
jusual@redhat.com,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Max Reitz" <mreitz@redhat.com>,
"Yury Kotov" <yury-kotov@yandex-team.ru>,
"Igor Mammedov" <imammedo@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: [RFC PATCH 0/1] Removing RAMBlocks during migration
Date: Tue, 7 Jan 2020 15:08:42 -0500 [thread overview]
Message-ID: <20200107150301-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200103114427.GD3804@work-vm>
On Fri, Jan 03, 2020 at 11:44:27AM +0000, Dr. David Alan Gilbert wrote:
> > 1) Guest: writes to slot's pci config
> > 2) QEMU: pcie_cap_slot_write_config -> pcie_unplug_device
> >
> > So, it's only guest driven action and qdev_unplug doesn't help here.
>
> Hmm we need to find a way to stop that; lets see if Michael Tsirkin has
> any ideas (cc'd) - I'm thinking if we could defer the unplug until the
> end of the migration we'd be OK; but it feels racy as to whether the
> destination is started with the device that the guest is unplugging.
>
> Dave
It's true - and same is possible with PCI, guest can remove device
at will.
Also, while libvirt learned not to start device del while migration
is active, it's annoying to have to wait for device del
to complete before migration can be started.
I guess we can make device invisible to guest - that concept
now exists because of failover, and can maybe be reused here.
Alternatively or additionally - for a while now I wanted to only remove
the device if guest powered it out and removal was requested. Again it
might be easier now that we have a concept of an invisible device.
--
MST
next prev parent reply other threads:[~2020-01-07 20:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-09 7:41 [RFC PATCH 0/1] Removing RAMBlocks during migration Yury Kotov
2019-12-09 7:41 ` [RFC PATCH 1/1] migration: Remove vmstate_unregister_ram Yury Kotov
2019-12-11 11:16 ` [RFC PATCH 0/1] Removing RAMBlocks during migration Dr. David Alan Gilbert
2019-12-23 8:51 ` Yury Kotov
2020-01-03 11:44 ` Dr. David Alan Gilbert
2020-01-07 20:08 ` Michael S. Tsirkin [this message]
2020-01-08 10:24 ` Dr. David Alan Gilbert
2020-01-13 14:18 ` Yury Kotov
2020-01-07 20:02 ` Michael S. Tsirkin
2020-01-08 13:40 ` Juan Quintela
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