Re: [Xen-users] matching Qemu version to Xen version, how critical?

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 10 Oct 2017, Ian Jackson wrote:
> Anthony, and Stefano, see below.  I haven't investigated at all.
> 
> Mark: I think you are probably fine to use the Debian version.

Yes, Ian is right.

In the past upstream QEMU didn't do a very good job at applying fixes to
stable trees, so I haven't been looking closely for changes there. In
fact, it often happened that the qemu-xen stable trees would have more
fixes than the corresponding QEMU stable trees.

It is very good to see that this has changed. Many fixes were applied to
qemu/stable-2.8, that today are not in qemu-xen/stable-4.9. But we can
start backporting now. Anthony, would you be up for watching the QEMU
stable trees more closely and backporting fixes from there to the
qemu-xen stable trees going forward?


> Mark Pryor writes ("Re: [Xen-users] matching Qemu version to Xen version, how 
> critical?"):
> > Hello,
> > 
> > https://paste.fedoraproject.org/paste/o15OrLa~PY98S3EPm6P-Ag/
> > 
> > https://tracker.debian.org/news/877656
> > 
> >  
> > on Oct 02, Debian-security released 8 fixes for qemu-2.8. In total there are
> > 46 patches since the release of qemu-2.8 on Jul 21.
> > 
> > As shown, in the fpaste, I applied these 46 to the upstream xen-4.9 tarball
> > while
> > trying to package in Stretch. All applied cleanly.
> > 
> > As a source of qemu fixes xen-4.9, I've looked here:
> > http://xenbits.xen.org/gitweb/?p=qemu-xen.git;a=shortlog;h=refs/heads/
> > staging-4.9
> > 
> > you can see there is only 1 fix since the release of xen-4.9.0 (Jun 27).
> > 
> > Any harm in using the debian-delta for qemu fixes? Should these be 
> > auto-tested
> > by xenproject?
> > 
> > PryMar56
> > 
> > On Thursday, October 5, 2017 3:51 AM, Ian Jackson 
> > <ian.jackson@xxxxxxxxxxxxx>
> > wrote:
> > 
> > 
> > Mark Pryor writes ("matching Qemu version to Xen version, how critical?"):
> > 
> > ...
> > > Please tell me it doesn't matter what version of qemu is used with
> > > Xen, as long as they are build together. How critical can it be?
> > 
> > 
> > It's not very critical, if you are using a released version of Xen.
> > In particular, if it builds, you're unlikely to go very far wrong.
> > 
> > NB though that (as you suggest from "built together") the Xen control
> > libraries that qemu uses 1. do not have a stable ABI until recently
> > (sorry) 2. do not have a stable interface to the hypervisor.
> > 
> > So unless you are using the very latest bits, you must rebuild when
> > you use a different Xen version.
> > 
> > Additionally, the qemu configure script works by determining the Xen
> > version (rather than by looking for individual features) and keying
> > everything off that.  So if you are using xen-unstable, you will find
> > that some qemu versions don't build.
 

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