Re: [Qemu-devel] [PATCH] [RFC] Add machine type pc-1.0-qemu-kvm for live migrate compatibility with qemu-kvm

[Alex Bligh]

On 22 Jul 2014, at 19:43, Alex Bligh <address@hidden> wrote:

> I have not (yet) brought forward the qxl rom size (and possibly
> video ram) changes in Cole's patches as I'd prefer an assessment
> of whether this is the right approach first.

Whilst vga=cirrus, and vga=none I appear to be able to get to work,
I suspect the QXL problem is unfixable.

The symptom on import is:
  Unknown ramblock "0000:00:02.0/virtio-net-pci.rom", cannot accept migration

A little debugging and this shows that the expected RAM blocks on load are
(just looking at the ones starting 0000:00):
   0000:00:02.0/qxl.vram
   0000:00:02.0/qxl.rom
   0000:00:03.0/virtio-net-pci.rom
   0000:00:02.0/qxl.vrom

note the 03 in virtio-net-pci.rom, not an 02.

Looking at the migrated file (from qemu-kvm-1.0 with a pc-1.0 machine type)
with 'strings', I see:
   0000:00:02.0/virtio-net-pci.rom
   0000:00:00.0/I440FX
   0000:00:01.0/PIIX3
   0000:00:02.0/virtio-net
   0000:00:01.1/ide
   0000:00:01.2/uhci
   0000:00:01.3/piix4_pm
   0000:00:03.0/virtio-blk

A migrated file (from qemu 2.0 with a pc-1.0-qemu-kvm machine type) has
   0000:00:02.0/qxl.vram
   0000:00:03.0/virtio-net-pci.rom
   0000:00:02.0/qxl.rom
   0000:00:02.0/qxl.vrom
   0000:00:00.0/I440FX
   0000:00:01.0/PIIX3
   0000:00:02.0/qxl
   0000:00:03.0/virtio-net
   0000:00:01.1/ide
   0000:00:01.2/uhci
   0000:00:01.3/piix4_pm
   0000:00:04.0/virtio-blk

The symptom is the result of the assignment of device number 03 to
virtio-net, as (it would seem) qxl does not actually have a pci
device id in qemu-kvm-1.0 (or at least not one making it to migration);
I'm assuming the names are PCI BDF. Hence virtio-net is getting
device ID 02 not 03.

QXL does appear to migrate qemu-kvm-1.0 to qemu-kvm-1.0. I'm guessing
that once upon a time QXL was not a PCI device, but it is now.

For once I don't think Cole Robinson's patch is going to help here
as this seems to be handling QXL rom size mismatches between 8k
and 16k, and the QXL romsize (on both ubuntu 12.04 and 14.04 is
well over 32k) so that looks like not the issue.

I suspect QXL on qemu-kvm-1.0 is a bit niche anyway.

-- 
Alex Bligh