linux-kernel - Re: [PATCH v4 5/6] KVM: MMU: combine guest pte read between walk and pte prefetch

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Message-ID: <20100702170303.GC25969@amt.cnet>
Date:	Fri, 2 Jul 2010 14:03:03 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH v4 5/6] KVM: MMU: combine guest pte read between walk and
 pte prefetch

On Thu, Jul 01, 2010 at 09:55:56PM +0800, Xiao Guangrong wrote:
> Combine guest pte read between guest pte walk and pte prefetch
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> ---
>  arch/x86/kvm/paging_tmpl.h |   48 ++++++++++++++++++++++++++++++-------------
>  1 files changed, 33 insertions(+), 15 deletions(-)

Can't do this, it can miss invlpg:

vcpu0			vcpu1
read guest ptes
			modify guest pte
			invlpg
instantiate stale 
guest pte

See how the pte is reread inside fetch with mmu_lock held.

Otherwise the patchset looks fine to me.

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