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Date: Mon, 28 Jan 2013 22:21:51 -0200
From: Marcelo Tosatti <mtosatti@redhat.com>
To: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Avi Kivity <avi.kivity@gmail.com>, Gleb Natapov <gleb@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 03/12] KVM: MMU: simplify mmu_set_spte
Message-ID: <20130129002151.GB10814@amt.cnet>
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On Wed, Jan 23, 2013 at 06:05:29PM +0800, Xiao Guangrong wrote:
> In order to detecting spte remapping, we can simply check whether the
> spte has already been pointing to the pfn even if the spte is not the
> last spte, for middle spte is pointing to the kernel pfn which can not
> be mapped to userspace

This check is detecting spte overwrite, when a large spte is replaced by 
pointer to spte table.

Can't see why check for different pfn is safe: only 'int level' can
differ, and pfn be equivalent, for example.