From patchwork Tue Aug 30 02:37:50 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiao Guangrong X-Patchwork-Id: 1111652 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.4) with ESMTP id p7U2Zxn2012337 for ; Tue, 30 Aug 2011 02:35:59 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752601Ab1H3Cfi (ORCPT ); Mon, 29 Aug 2011 22:35:38 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:51019 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752577Ab1H3Cfh (ORCPT ); Mon, 29 Aug 2011 22:35:37 -0400 Received: from tang.cn.fujitsu.com (tang.cn.fujitsu.com [10.167.250.3]) by song.cn.fujitsu.com (Postfix) with ESMTP id 8F76917013E; Tue, 30 Aug 2011 10:35:36 +0800 (CST) Received: from mailserver.fnst.cn.fujitsu.com (tang.cn.fujitsu.com [127.0.0.1]) by tang.cn.fujitsu.com (8.14.3/8.13.1) with ESMTP id p7U2Za41010313; Tue, 30 Aug 2011 10:35:36 +0800 Received: from localhost.localdomain ([10.167.225.99]) by mailserver.fnst.cn.fujitsu.com (Lotus Domino Release 8.5.1FP4) with ESMTP id 2011083010343801-33512 ; Tue, 30 Aug 2011 10:34:38 +0800 Message-ID: <4E5C4CFE.20307@cn.fujitsu.com> Date: Tue, 30 Aug 2011 10:37:50 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Avi Kivity CC: Marcelo Tosatti , LKML , KVM Subject: [PATCH v3 10/11] KVM: MMU: fix detecting misaligned accessed References: <4E5C4C20.3000403@cn.fujitsu.com> In-Reply-To: <4E5C4C20.3000403@cn.fujitsu.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-08-30 10:34:38, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-08-30 10:34:38, Serialize complete at 2011-08-30 10:34:38 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Tue, 30 Aug 2011 02:36:00 +0000 (UTC) Sometimes, we only modify the last one byte of a pte to update status bit, for example, clear_bit is used to clear r/w bit in linux kernel and 'andb' instruction is used in this function, in this case, kvm_mmu_pte_write will treat it as misaligned access, and the shadow page table is zapped Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index cfe24fe..adaa160 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -3601,6 +3601,14 @@ static bool detect_write_misaligned(struct kvm_mmu_page *sp, gpa_t gpa, offset = offset_in_page(gpa); pte_size = sp->role.cr4_pae ? 8 : 4; + + /* + * Sometimes, the OS only writes the last one bytes to update status + * bits, for example, in linux, andb instruction is used in clear_bit(). + */ + if (!(offset & (pte_size - 1)) && bytes == 1) + return false; + misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1); misaligned |= bytes < 4;