From: George Dunlap <george.dunlap@citrix.com>
To: Ian Jackson <Ian.Jackson@eu.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: Tue, 7 Jun 2016 15:08:06 +0100 [thread overview]
Message-ID: <5756D546.9000609@citrix.com> (raw)
In-Reply-To: <22353.28127.934683.210436@mariner.uk.xensource.com>
On 03/06/16 12:45, Ian Jackson wrote:
> 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.
Why in the Deprecated section?
The current interface is a bit mad. I've just been running my CentOS
smoke-testing scripts against packages built against 4.7-rc4. I've got
bits of the scripts which mount filesystems in dom0; bits of it that do
bits in fstab and so on, and bits of it that actually generate the
config file.
In every part of the whole system -- in dom0, in the guest, in
everything -- I use xvda; *except* in the parts dealing with the guest
config, where for some reason I mysteriously put 'hda', which ends up
producing an xvda either when booted PV or when booted HVM. Does that
make any sense?
What about a per-disk property, emulate={default,always,only}, which for
HVM will do the things we're talking about and be ignored on PV?
'default' will behave as it does now: xvda will get you only PV, hda
will get you PV-backed emulated. 'always' will always give you an
emulated device even if you specify xvda, and 'only' will only give you
an emulated device (with no PV).
I actually think the default for most people who are not using EFI would
be to include "vdev=xvd?,emulate=always" in most config files for
maximum flexibility and consistency.
-George
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-06-07 14:08 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5756D546.9000609@citrix.com \
--to=george.dunlap@citrix.com \
--cc=Ian.Jackson@eu.citrix.com \
--cc=Wei.Liu2@citrix.com \
--cc=anthony.perard@citrix.com \
--cc=olaf@aepfle.de \
--cc=xen-devel@lists.xen.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).