linux-kernel - Re: [PATCH] x86, kvm: Add MSR_AMD64_BU

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Message-ID: <20130213121002.GD9817@redhat.com>
Date:	Wed, 13 Feb 2013 14:10:02 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Borislav Petkov <bp@...en8.de>, kvm@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Boris Ostrovsky <boris.ostrovsky@....com>,
	Andre Przywara <andre@...rep.de>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH] x86, kvm: Add MSR_AMD64_BU_CFG2 to the list of ignored
 MSRs

On Wed, Feb 13, 2013 at 12:55:26PM +0100, Borislav Petkov wrote:
> On Wed, Feb 13, 2013 at 01:47:47PM +0200, Gleb Natapov wrote:
> > On Wed, Feb 13, 2013 at 12:42:41PM +0100, Borislav Petkov wrote:
> > > From: Borislav Petkov <bp@...e.de>
> > > 
> > > The "x86, AMD: Enable WC+ memory type on family 10 processors" patch
> > > currently in -tip added a workaround for AMD F10h CPUs which #GPs my
> > > guest when booted in kvm. This is because it accesses MSR_AMD64_BU_CFG2
> > > which is not currently ignored by kvm. Do that because this MSR is only
> > > baremetal-relevant anyway. While at it, move the ignored MSRs at the
> > > beginning of kvm_set_msr_common so that we exit then and there.
> > > 
> > Is your guest compiled without PV support? With PV Linux traps #GP for
> > all MSRs and it saves us in more than one places.
> 
> Yes, CONFIG_PARAVIRT_GUEST is not set on the guest kernel.
> 
Thanks. It does not mean that the patch should not be applied though.
I cannot seems to find the documentation for the MSR anywhere, do you
have a pointer?

--
			Gleb.
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