linux-kernel - Re: [Xen-devel] [PATCH/RFC] Fix xsave bug on older Xen hypervisors

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Message-ID: <504B1B58.4030103@redhat.com>
Date:	Sat, 08 Sep 2012 12:18:00 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	"Justin M. Forbes" <jmforbes@...uxtx.org>,
	Jan Beulich <JBeulich@...e.com>,
	Stefan Bader <stefan.bader@...onical.com>,
	Matt Wilson <msw@...zon.com>, xen-devel@...ts.xen.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH/RFC] Fix xsave bug on older Xen hypervisors

Il 07/09/2012 16:54, Konrad Rzeszutek Wilk ha scritto:
>>> But iirc that bad patch is a Linux side one (i.e. you're trying to fix
>>> something upstream that isn't upstream)?
>>>
>> Right, so the patch that this improves upon, and that Fedora and Ubuntu are
>> currently carrying is not upstream because:
>>
>> a) It's crap, it cripples upstream xen users, but doesn't impact RHEL xen
>> users because xsave was never supported there.
>>
>> b) The hypervisor was patched to make it unnecessary quite some time ago,
>> and we hoped EC2 would eventually pick up that correct patch and we could
>> drop the crap kernel patch.
>>
>> Unfortunately this has not happened. We are at a point where EC2 really is
>> a quirk that has to be worked around. Distros do not want to maintain
>> a separate EC2 build of the kernel, so the easiest way is to cripple
>> current upstream xen users.  This quirk is unfortunately the best possible
>> solution.  Having it upstream also makes it possible for any user to build
>> an upstream kernel that will run on EC2 without having to dig a random
>> patch out of a vendor kernel.
> 
> Sure. Jan is asking though for actual confirmation that the upstream kernel
> does indeed go belly up without a workaround.
> And whether this patch (which I would did since Canonical is carrying it) does
> fix the issue.
> 
> I am still a newbie on the Amazon EC2 upload your kernel thing (hint, would
> appreciate somebody taking this patch and trying it out).

You can just pick an old version of the CentOS kernel package, for
example 2.6.18-128.el5 or 2.6.18-164.el5 (respectively CentOS/RHEL 5.3
and 5.4).

Paolo

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