linux-kernel - Re: [Xen-devel] [PATCH] x86/amd: fix crash as Xen Dom0 on AMD Trinity systems

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Date:	Wed, 30 May 2012 17:12:36 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Jan Beulich <JBeulich@...e.com>,
	Andre Przywara <andre.przywara@....com>,
	Jacob Shin <Jacob.Shin@....com>, mingo@...e.hu,
	jeremy@...p.org, tglx@...utronix.de, xen-devel@...ts.xensource.com,
	linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] x86/amd: fix crash as Xen Dom0 on AMD
 Trinity systems

On Wed, May 30, 2012 at 10:49:29AM -0400, Konrad Rzeszutek Wilk wrote:
> On Wed, May 30, 2012 at 07:42:56AM -0700, H. Peter Anvin wrote:
> > On 05/30/2012 07:23 AM, Jan Beulich wrote:
> > > 
> > > I see - the Xen code blindly overwrites pv_cpu_ops, despite not
> > > having initialized all members. That's an obvious oversight of the
> > > patch that introduced the _regs variants.
> > > 
> > > Plus having secondary instances of things like rdmsrl_amd_safe()
> > > in asm/paravirt.h seems pretty strange an approach (which was
> > > why initially I didn't spot how a crash could happen there) - only
> > > the lowest level functions should get re-implemented here.
> > > 
> > 
> > This kinds of things are part of why Xen makes me want to cry regularly.
> 
> It looks like an oversight by Borislav (177fed1ee8d727c39601ce9fc2299b4cb25a718e
> and 132ec92f) and Yinghai (b05f78f5c713eda2c34e495d92495ee4f1c3b5e1) where
> they added these wrappers way back in 2009!

This is exactly why xen has nothing to do in arch/x86/. It is not an
oversight - I simply didn't test it on xen because I don't care about
it.

Remember our last discussion about mcelog?

This current case should be a perfect example for why xen shouldn't be
sprinkling code all over the place.

-- 
Regards/Gruss,
Boris.
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