From: Ian Jackson <Ian.Jackson@eu.citrix.com>
To: George Dunlap <george.dunlap@citrix.com>
Cc: Anthony Perard <anthony.perard@citrix.com>,
Olaf Hering <olaf@aepfle.de>, Wei Liu <Wei.Liu2@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: Fri, 3 Jun 2016 12:45:35 +0100 [thread overview]
Message-ID: <22353.28127.934683.210436@mariner.uk.xensource.com> (raw)
In-Reply-To: <575169B7.9060603@citrix.com>
George Dunlap writes ("Re: [Xen-devel] 4.7 qemu regression: HVM guests fail to boot from xvda"):
> On 03/06/16 12:20, Olaf Hering wrote:
> > I think the regression is: 'vdev=xvda' does not result in a disk
> > connected to the emulated controller. Should we change the way hdtype=
> > is handled internally? If hdtype= is not given it remains unset and with
> > vdev=xvd* no disk-on-emulated-controller gets added. If hdtype= is set
> > then vdev=xvd* will result in an disk-on-emulated-controller, which
> > fixes the regression. If vdev=hd* and hdtype= was not set, hdtype will
> > be silently set to ide.
>
> I'd be OK with this. But is the "hdtype unset" also available at the
> libxl level?
There are two problems with this `hdtype' approach.
Firstly, it is global. That is, it applies to all disks of the
particular guest. But then maybe we don't care about that because
this anomalous major-number-stealing behaviour is probably per-guest
rather than per-disk.
Secondly, the proposal above involves changing both the semantics of
existing `hdtype' parameter values, and the default hdtype value. The
resulting situation would be that even specifying vdev=hda wouldn't
get you an emulated device, by default, unless you specified `hdtype'
too. I don't think that is right.
The possibilities I see are:
(1) New boolean per-guest parameter for this behaviour, meaning
`provide emulated devices for all xvd* as if they were hd*'.
(2) New `hdtype=ideforpv' which has the same effect as `hdtype=ide'
plus the semantics in (1) above. (I'm open to better naming
suggestions.)
(3) New disk property parameter `hvm-emulate' in the Deprecated
section of xl-disk-configuration.txt.
Open questions:
Do we also need `... as if they were sd*' or `provide ide emulated
devices where vdev=sd* is specified?'
If we have `hdtype=ideinclpv' do we also need `hdtype=ahciinclpv' ?
What should happen if these options are enabled for PV guests - should
they be silently ignored, or should they be rejected ?
Ian.
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next prev parent reply other threads:[~2016-06-03 11:45 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 20:42 4.7 qemu regression: HVM guests fail to boot from xvda Olaf Hering
2016-05-31 11:02 ` George Dunlap
2016-05-31 11:16 ` Olaf Hering
2016-05-31 11:32 ` George Dunlap
2016-05-31 11:41 ` Olaf Hering
2016-05-31 12:00 ` George Dunlap
2016-05-31 12:04 ` Olaf Hering
2016-06-01 13:17 ` Olaf Hering
2016-06-01 21:40 ` Olaf Hering
2016-06-02 11:49 ` Wei Liu
2016-06-02 12:06 ` Olaf Hering
2016-05-31 12:15 ` Jan Beulich
2016-06-01 9:48 ` Wei Liu
2016-06-01 13:34 ` Olaf Hering
2016-06-01 14:11 ` Wei Liu
2016-06-01 14:32 ` Olaf Hering
2016-06-01 15:36 ` Ian Jackson
2016-06-03 10:13 ` George Dunlap
2016-06-03 11:20 ` Olaf Hering
2016-06-03 11:27 ` George Dunlap
2016-06-03 11:45 ` Ian Jackson [this message]
2016-06-06 10:39 ` George Dunlap
2016-06-06 10:52 ` Ian Jackson
2016-06-06 11:43 ` George Dunlap
2016-06-06 12:49 ` George Dunlap
2016-06-07 14:08 ` George Dunlap
2016-06-07 14:27 ` Olaf Hering
2016-06-08 10:17 ` Ian Jackson
2016-06-07 19:06 ` Olaf Hering
2016-06-08 10:18 ` Ian Jackson
2016-06-08 10:23 ` George Dunlap
2016-06-08 10:30 ` Ian Jackson
2016-06-08 10:49 ` George Dunlap
2016-06-08 11:13 ` Olaf Hering
2016-06-08 15:56 ` Konrad Rzeszutek Wilk
2016-06-03 11:50 ` Olaf Hering
2016-05-31 12:10 ` Jan Beulich
2016-05-31 13:41 ` George Dunlap
2016-05-31 14:10 ` Jan Beulich
2016-05-31 16:15 ` Konrad Rzeszutek Wilk
2016-06-08 11:38 ` Wei Liu
2016-06-08 12:04 ` Olaf Hering
2016-06-08 12:09 ` Wei Liu
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