From patchwork Wed Jun 19 09:09:25 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Xiao Guangrong X-Patchwork-Id: 2748101 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 255969F39E for ; Wed, 19 Jun 2013 09:10:56 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 18577202DF for ; Wed, 19 Jun 2013 09:10:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E6F85202DD for ; Wed, 19 Jun 2013 09:10:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934463Ab3FSJKt (ORCPT ); Wed, 19 Jun 2013 05:10:49 -0400 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:41536 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934299Ab3FSJJu (ORCPT ); Wed, 19 Jun 2013 05:09:50 -0400 Received: from /spool/local by e28smtp08.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 19 Jun 2013 14:31:24 +0530 Received: from d28dlp03.in.ibm.com (9.184.220.128) by e28smtp08.in.ibm.com (192.168.1.138) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Wed, 19 Jun 2013 14:31:22 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id 677161258043; Wed, 19 Jun 2013 14:38:43 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r5J99sSg16253144; Wed, 19 Jun 2013 14:39:54 +0530 Received: from d28av04.in.ibm.com (loopback [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r5J99h7B026296; Wed, 19 Jun 2013 19:09:44 +1000 Received: from localhost (ericxiao.cn.ibm.com [9.111.29.143]) by d28av04.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id r5J99guR026202; Wed, 19 Jun 2013 19:09:42 +1000 From: Xiao Guangrong To: gleb@redhat.com Cc: avi.kivity@gmail.com, mtosatti@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Xiao Guangrong Subject: [PATCH 7/7] KVM: MMU: document fast invalidate all mmio sptes Date: Wed, 19 Jun 2013 17:09:25 +0800 Message-Id: <1371632965-20077-8-git-send-email-xiaoguangrong@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1371632965-20077-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> References: <1371632965-20077-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13061909-2000-0000-0000-00000C8DB657 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-8.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Document it to Documentation/virtual/kvm/mmu.txt Signed-off-by: Xiao Guangrong --- Documentation/virtual/kvm/mmu.txt | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt index f5c4de9..9b7cfb3 100644 --- a/Documentation/virtual/kvm/mmu.txt +++ b/Documentation/virtual/kvm/mmu.txt @@ -396,6 +396,31 @@ ensures the old pages are not used any more. The invalid-gen pages (sp->mmu_valid_gen != kvm->arch.mmu_valid_gen) are zapped by using lock-break technique. +Fast invalidate all mmio sptes +=========== +As mentioned in "Reaction to events" above, kvm will cache the mmio information +to the last sptes so that we should zap all mmio sptes when the guest mmio info +is changed. This will happen when a new memslot is added or the existing +memslot is moved. + +Zapping mmio spte is also a scalability issue for the large memory and large +vcpus guests since it needs to hold hot mmu-lock and walk all shadow pages to +find all the mmio spte out. + +We fix this issue by using the similar way of "Fast invalidate all pages". +The global mmio valid generation-number is stored in kvm->memslots.generation +and every mmio spte stores the current global generation-number into his +available bits when it is created + +The global mmio valid generation-number is increased whenever the gust memory +info is changed. When guests do mmio access, kvm intercepts a MMIO #PF then it +walks the shadow page table and get the mmio spte. If the generation-number on +the spte does not equal the global generation-number, it will go to the normal +#PF handler to update the mmio spte. + +Since 19 bits are used to store generation-number on mmio spte, we zap all pages +when the number is round. + Further reading ===============