Re: 4.7 qemu regression: HVM guests fail to boot from xvda

From: Olaf Hering <olaf@aepfle.de>
To: Wei Liu <wei.liu2@citrix.com>
Cc: Anthony Perard <anthony.perard@citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: 4.7 qemu regression: HVM guests fail to boot from xvda
Date: Thu, 2 Jun 2016 14:06:40 +0200	[thread overview]
Message-ID: <20160602120640.GA21686@aepfle.de> (raw)
In-Reply-To: <20160602114916.GV5160@citrix.com>

On Thu, Jun 02, Wei Liu wrote:

> On Wed, Jun 01, 2016 at 11:40:51PM +0200, Olaf Hering wrote:
> > tool_ver  vdev_str  qemu   format  usable  bootable
> > xen-4.5     xvd     qmain   qcow2   yes     SUSE:no, staging:yes
> What does "staging" mean?

That should have been staging-4.5.
Some change between our 4.5.1 and 4.5.2 based toolstack broke xvd booting.

> > xen-4.6     xvd     qmain    raw    yes     yes
> > xen-4.6     xvd     qmain   qcow2   yes     yes

> > xen-4.7     xvd     qmain    raw    yes     no
> > xen-4.7     xvd     qmain   qcow2   yes     no

> So the last column only apply to xenlinux kernel?

The relevant row is 'bootable', thats where the regression is. It means
'BIOS finds a disk, can access it and run bootloader'. In my testing the
BIOS did not see a disk, just the 'cdrom' had in domU.cfg as well.

'usable' means a PV driver may actually access the given device. This is
always the case, except qemu-trad has no qcow2 support.

> I expect pvops to be all "yes" because it doesn't use vdev_str. I also
> expect freebsd to work because it parses vbd number and translates that
> to freebsd-speak device identifier.

This list has no column 'makes use of vdev_str' because the list does not
describe domU OS behaviour. ;-)

See my other mail regarding domU os. If we leave xen-4.7 as is then
domU.cfg has to be changed from 'xvd' to 'hd' to allow BIOS boot again.
This will change things for (at least) xenlinux based kernels because
the kernel device name change. I think this needs adjustments to
/boot/grub/device.map and /etc/default/grub_installdevice. The latter is
an odd SUSE thing, describing where grub2 should write things, its
likely similar to device.map.

fstab and root= can be changed to use on-disk identifiers like UUID or
LABEL to work with either xvd or hd. LVM or raid might be unaffected.

Eventually there are more places which need adjustment, like autoinstall
profiles.

Olaf

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