From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v6 5/9] KVM: MMU: introduce SPTE_MMU_WRITEABLE bit
Date: Tue, 12 Jun 2012 23:01:03 -0300
Message-ID: <20120613020103.GB3119@amt.cnet>
References: <4FC470C7.5040700@linux.vnet.ibm.com>
 <4FC4716A.8030304@linux.vnet.ibm.com>
 <20120611233212.GA29573@amt.cnet>
 <4FD6A833.6060206@linux.vnet.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Avi Kivity <avi@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
	KVM <kvm@vger.kernel.org>
To: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <4FD6A833.6060206@linux.vnet.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On Tue, Jun 12, 2012 at 10:23:47AM +0800, Xiao Guangrong wrote:
> On 06/12/2012 07:32 AM, Marcelo Tosatti wrote:
> 
> > On Tue, May 29, 2012 at 02:49:14PM +0800, Xiao Guangrong wrote:
> >> This bit indicates whether the spte can be writable on MMU, that means
> >> the corresponding gpte is writable and the corresponding gfn is not
> >> protected by shadow page protection
> > 
> > Why is this still necessary, now that only sptes of direct shadow pages 
> > are updated locklessly? 
> > 
> 
> 
> Yes, but it is still needed, for nested npt/ept, we need protect
> the nested page tables.

Sure, but shadowed L1 nested pagetables are not direct shadow pages.

They are shadows of L1 nested pagetables. 

Checking sp->direct should be enough (instead of the flags).