linux-kernel - Re: [PATCH 11/11] KVM: MMU: improve write flooding detected

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Message-ID: <4E2FF1AA.3020507@redhat.com>
Date:	Wed, 27 Jul 2011 14:08:26 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 11/11] KVM: MMU: improve write flooding detected

On 07/27/2011 01:20 PM, Xiao Guangrong wrote:
> >>    }
> >
> >  I think this is a little dangerous.  A guest kernel may be instantiating multiple gptes on a page fault, but guest userspace hits only one of them (the one which caused the page fault) - I think Windows does this, but I'm not sure.
> >
>
> I think this case is not bad: if the guest kernel need to write multiple gptes (>=3),
> it will cause many page fault, we do better zap the shadow page and let it become writable as
> soon as possible.
> (And, we have pte-fetch, it can quickly establish the mapping for a new shadow page)

Actually, what should save us is unsync pages.  Why are we hitting this 
path at all?

-- 
error compiling committee.c: too many arguments to function

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