From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH 11/11] KVM: MMU: improve write flooding detected
Date: Thu, 25 Aug 2011 10:21:11 -0300
Message-ID: <20110825132110.GA4384@amt.cnet>
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Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
	LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
To: Avi Kivity <avi@redhat.com>
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On Thu, Aug 25, 2011 at 07:42:10AM +0300, Avi Kivity wrote:
> On 08/25/2011 05:04 AM, Marcelo Tosatti wrote:
> >>
> >>  It could increase the flood count independently of the accessed bit of
> >>  the spte being updated, zapping after 3 attempts as it is now.
> >>
> >>  But additionally reset the flood count if the gpte appears to be valid
> >>  (points to an existant gfn if the present bit is set, or if its zeroed).
> >
> >Well not zero, as thats a common pattern for non ptes.
> >
> 
> On 32-bit with 4GB RAM, practically anything is a valid gpte.

The following could be required to consider a valid gpte, for write
flood detection purposes:

- Must be present.
- PageCacheDisable must be unset.
- PageWriteThrough must be unset.