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

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Message-ID: <4FC633A7.1050406@zytor.com>
Date:	Wed, 30 May 2012 07:50:15 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Andre Przywara <andre.przywara@....com>, mingo@...e.hu,
	tglx@...utronix.de, jeremy@...p.org, xen-devel@...ts.xensource.com,
	stable@...r.kernel.org#3.4+, linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] x86/amd: fix crash as Xen Dom0 on AMD Trinity
 systems

On 05/30/2012 07:39 AM, Konrad Rzeszutek Wilk wrote:
> On Wed, May 30, 2012 at 03:10:02PM +0200, Andre Przywara wrote:
>> Because we are behind a family check before tweaking the topology
>> bit, we can use the standard rd/wrmsr variants for the CPUID feature
>> register.
>> This fixes a crash when using the kernel as a Xen Dom0 on affected
>> Trinity systems. The wrmsrl_amd_safe is not properly paravirtualized
>> yet (this will be fixed in another patch).
> 
> So with a rdmsrl_amd_safe and wrmsrl_amd_safe being implemented in
> the pv_cpu_ops - would this patch even be neccessary?
> 

That is still bogus;  a better thing would be to implement the _regs
interface.  Even better would be to trap and emulate rdmsr/wrmsr!

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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