From mboxrd@z Thu Jan  1 00:00:00 1970
From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Subject: Re: [PATCH v5 11/14] nEPT: MMU context for nested EPT
Date: Thu, 01 Aug 2013 17:51:14 +0800
Message-ID: <51FA2F92.5050107@linux.vnet.ibm.com>
References: <1375282131-9713-1-git-send-email-gleb@redhat.com> <1375282131-9713-12-git-send-email-gleb@redhat.com> <51FA2757.2030602@linux.vnet.ibm.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Cc: Gleb Natapov <gleb@redhat.com>, kvm@vger.kernel.org,
	Jun Nakajima <jun.nakajima@intel.com>,
	Yang Zhang <yang.z.zhang@intel.com>, pbonzini@redhat.com
To: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Return-path: <kvm-owner@vger.kernel.org>
Received: from e23smtp01.au.ibm.com ([202.81.31.143]:47455 "EHLO
	e23smtp01.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752459Ab3HAJvW (ORCPT <rfc822;kvm@vger.kernel.org>);
	Thu, 1 Aug 2013 05:51:22 -0400
Received: from /spool/local
	by e23smtp01.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted
	for <kvm@vger.kernel.org> from <xiaoguangrong@linux.vnet.ibm.com>;
	Thu, 1 Aug 2013 19:41:28 +1000
Received: from d23relay03.au.ibm.com (d23relay03.au.ibm.com [9.190.235.21])
	by d23dlp02.au.ibm.com (Postfix) with ESMTP id 577F02BB0051
	for <kvm@vger.kernel.org>; Thu,  1 Aug 2013 19:51:18 +1000 (EST)
Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96])
	by d23relay03.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r719p8oK60489946
	for <kvm@vger.kernel.org>; Thu, 1 Aug 2013 19:51:08 +1000
Received: from d23av01.au.ibm.com (localhost [127.0.0.1])
	by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id r719pH4r010767
	for <kvm@vger.kernel.org>; Thu, 1 Aug 2013 19:51:17 +1000
In-Reply-To: <51FA2757.2030602@linux.vnet.ibm.com>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

On 08/01/2013 05:16 PM, Xiao Guangrong wrote:
> On 07/31/2013 10:48 PM, Gleb Natapov wrote:
>> From: Nadav Har'El <nyh@il.ibm.com>
>>
>> KVM's existing shadow MMU code already supports nested TDP. To use it, we
>> need to set up a new "MMU context" for nested EPT, and create a few callbacks
>> for it (nested_ept_*()). This context should also use the EPT versions of
>> the page table access functions (defined in the previous patch).
>> Then, we need to switch back and forth between this nested context and the
>> regular MMU context when switching between L1 and L2 (when L1 runs this L2
>> with EPT).
> 
> This patch looks good to me.
> 
> Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
> 
> But i am confused that update_permission_bitmask() is not adjusted in this
> series. That function depends on kvm_read_cr4_bits(X86_CR4_SMEP) and
> is_write_protection(), these two functions should read the registers from
> L2 guest, using the L2 status to check L1's page table seems strange.
> The same issue is in nested npt. Anything i missed?

After check the code, i found vcpu->arch.mmu is not updated when switch to
nested mmu, that means, "using the L2 status to check L1's page table seems
strange" is wrong. That is fine on nested npt, but nested ept should adjust
the logic anyway.