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Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migratio
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream |
Date: |
Thu, 15 May 2014 10:14:46 +0300 |
On Thu, May 15, 2014 at 12:16:35PM +0530, Amit Shah wrote:
> On (Thu) 15 May 2014 [09:23:51], Michael S. Tsirkin wrote:
> > On Thu, May 15, 2014 at 11:34:25AM +0530, Amit Shah wrote:
> > > On (Wed) 14 May 2014 [17:41:38], Greg Kurz wrote:
> > > > There is a need to add some more fields to VirtIODevice that should be
> > > > migrated (broken status, endianness). The problem is that we do not
> > > > want to break compatibility while adding a new feature... This issue has
> > > > been addressed in the generic VMState code with the use of optional
> > > > subsections. As a *temporary* alternative to port the whole virtio
> > > > migration code to VMState, this patch mimics a similar subsectionning
> > > > ability for virtio.
>
> BTW Greg, do you plan on working on vmstate for virtio?
>
> > > > Since each virtio device is streamed in its own section, the idea is to
> > > > stream subsections between the end of the device section and the start
> > > > of the next sections. This allows an older QEMU to complain and exit
> > > > when fed with subsections:
> > > >
> > > > Unknown savevm section type 5
> > > > Error -22 while loading VM state
> > >
> > > Please make this configurable -- either via configure or device
> > > properties. That avoids having to break existing configurations that
> > > work without this patch.
> > >
> > > > All users of virtio_load()/virtio_save() need to be patched because the
> > > > subsections are streamed AFTER the device itself.
> > >
> > > Since all have the same fixup, I'm wondering if a new section can be
> > > added to the virtio-bus itself, which gets propagated to all devices
> > > upon load in the dest.
> >
> > This calls for a way for devices to inherit properties from the bus,
> > which doesn't exist ATM.
> > Fine but let's not hold up this patchset because of this.
>
> No, only suggestion is to add a migration section in the bus, and then
> it's easier to do this in the post-migrate functions for each device
> -- so only one new section gets introduced instead of all devices
> being modified to send a new subsection.
>
> Amit
I don't mind but the gain isn't very big here.
--
MST
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, (continued)
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Greg Kurz, 2014/05/15
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Fam Zheng, 2014/05/16
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Andreas Färber, 2014/05/16
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Fam Zheng, 2014/05/16
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Greg Kurz, 2014/05/16
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Michael S. Tsirkin, 2014/05/17
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Greg Kurz, 2014/05/15
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Amit Shah, 2014/05/15
- Re: [Qemu-devel] [PATCH RFC 1/8] virtio: add subsections to the migration stream, Michael S. Tsirkin, 2014/05/15
[Qemu-devel] [PATCH RFC 2/8] virtio-net: migrate subsections, Greg Kurz, 2014/05/14
[Qemu-devel] [PATCH RFC 3/8] virtio-blk: migrate subsections, Greg Kurz, 2014/05/14
[Qemu-devel] [PATCH RFC 4/8] virtio-scsi: migrate subsections, Greg Kurz, 2014/05/14
[Qemu-devel] [PATCH RFC 5/8] virtio-serial: migrate subsections, Greg Kurz, 2014/05/14
[Qemu-devel] [PATCH RFC 6/8] virtio-balloon: migrate subsections, Greg Kurz, 2014/05/14
[Qemu-devel] [PATCH RFC 7/8] virtio-rng: migrate subsections, Greg Kurz, 2014/05/14
[Qemu-devel] [PATCH RFC 8/8] virtio: add endian-ambivalent support to VirtIODevice, Greg Kurz, 2014/05/14