linux-kernel - Re: commit 3c2e7f7de3 (KVM use NPT page attributes) causes boot failures

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Date:	Wed, 2 Sep 2015 11:38:18 +0200
From:	Markus Trippelsdorf <markus@...ppelsdorf.de>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>, Joerg Roedel <jroedel@...e.de>,
	Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Subject: Re: commit 3c2e7f7de3 (KVM use NPT page attributes) causes boot
 failures

On 2015.09.02 at 17:17 +0800, Xiao Guangrong wrote:
> >
> > No. PAT is of course enabled and booting is successful sometimes even
> > with the BUG() in allback_mtrr_type(). I suspect a setup (timing) issue.
> 
> Thanks for your confirmation.
> 
> >
> > markus@x4 linux % cat .config | grep  X86_PAT
> > CONFIG_X86_PAT=y
> > markus@x4 linux % dmesg | grep PAT
> > [    0.000000] x86/PAT: Configuration [0-7]: WB  WC  UC- UC  WB  WC  UC- WT
> 
> Strange, BP processor has already set WC to PAT1, however KVM does not read it out
> from PAT MSR on its local CPU.
> 
> Hmm... PAT default values do not include WC, it seems initing PAT on SP has not
> finished after module_init()?
> 
> Could please apply this diff and test it again?

(Your patch was malformed.)

[    2.138098] kvm: Nested Virtualization enabled
[    2.138153] kvm: Nested Paging enabled
[    2.138204] KVM PAT: 0x7040600070406.
[    2.138255] mtrr2protval[0]:18.
[    2.138306] mtrr2protval[1]:ff.
[    2.138356] mtrr2protval[2]:0.
[    2.138408] mtrr2protval[3]:0.
[    2.138459] mtrr2protval[4]:8.
[    2.138510] mtrr2protval[5]:ff.
[    2.138561] mtrr2protval[6]:0.
[    2.138612] mtrr2protval[7]:10.
[    2.138662] BUG in fallback_mtrr_type, mtrr = 1.

-- 
Markus
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