linux-kernel - Re: [PATCH v3 07/15] KVM: MMU: introduce nulls desc

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Message-ID: <20131125101943.GS2108@redhat.com>
Date:	Mon, 25 Nov 2013 12:19:43 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Marcelo Tosatti <mtosatti@...hat.com>, avi.kivity@...il.com,
	"pbonzini@...hat.com Bonzini" <pbonzini@...hat.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Eric Dumazet <dada1@...mosbay.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 07/15] KVM: MMU: introduce nulls desc

On Mon, Nov 25, 2013 at 02:11:31PM +0800, Xiao Guangrong wrote:
> > 
> > For example, nothing prevents lockless walker to move into some
> > parent_ptes chain, right?
> 
> No.
> 
> The nulls can help us to detect this case, for parent_ptes, the nulls points
> to "shadow page" but for rmaps, the nulls points to slot.arch.rmap. There
> is no chance that the “rmap" is used as shadow page when slot-lock is held.
> 
But meanwhile we will write protect non-last level sptes, no? Better to
create separate slab caches for rmap and parent_ptes lists.

--
			Gleb.
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