[Pkg-libvirt-maintainers] Bug#773189: Bug#773189: libvirt-daemon: Haswell microcode update breaks CPU detection
agx at sigxcpu.org
Sat Dec 20 10:27:18 UTC 2014
On Tue, Dec 16, 2014 at 01:34:12PM +0100, Guido Günther wrote:
> On Mon, Dec 15, 2014 at 06:56:19PM +0100, intrigeri wrote:
> > hi,
> > Chris Boot wrote (15 Dec 2014 12:39:52 GMT) :
> > > The intel-microcode 3.20140913.1 update disables TSX-NI (transactional
> > > memory instructions). When a server running libvirt is rebooted with
> > > this update, libvirt no longer considers the machine to have a Haswell
> > > CPU:
> > > dietrich ~ # virsh capabilities | grep -A1 '<arch>x86_64'
> > > <arch>x86_64</arch>
> > > <model>SandyBridge</model>
> > > This causes a problem as any VMs that require a Haswell CPU, which would
> > > have worked previously, now fail to start altogether. Commenting out the
> > > two cpuinfo flags relevant to TSX-NI from /usr/share/libvirt/cpu_map.xml
> > > fixes this for me:
> > FWIW, I've been suffering from the symptoms of that issue for a few
> > weeks. I guessed it was caused by that microcode update, but had no
> > time to report it. *If* that's a regression since Wheezy, I think
> > it would qualify as RC, since VMs that started just fine previously
> > now fail to come up at boot. The workaround (in the package) is tiny,
> > and makes sense to me: if Intel themselves now consider that Haswell
> > CPUs have no TSX-NI, then libvirt's view of what's a Haswell CPU
> > should be updated.
> > OTOH, the user-side workaround (copy host CPU model) is easy enough
> > too, although a bit painful to discover initially for many users
> > I guess.
> > Shall we ask the release team if they would happily unblock this
> > change for Jessie?
> I think we should. I've submitted it upstream to get some feadback and
> make this a safe change and thanks to both of you!
Following upstream's reasoning:
I'm inclinded to tag this wontfix since we'd otherwise change
behaviour in regard to other distros. We could add a HaswellDebian2
in ase we want that featureset codified as well.
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