Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934585Ab3FSJNi (ORCPT ); Wed, 19 Jun 2013 05:13:38 -0400 Received: from e28smtp02.in.ibm.com ([122.248.162.2]:39674 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934316Ab3FSJJo (ORCPT ); Wed, 19 Jun 2013 05:09:44 -0400 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 3/7] KVM: MMU: document write_flooding_count Date: Wed, 19 Jun 2013 17:09:21 +0800 Message-Id: <1371632965-20077-4-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: 13061909-5816-0000-0000-00000884150F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1981 Lines: 51 Document write_flooding_count to Documentation/virtual/kvm/mmu.txt Signed-off-by: Xiao Guangrong --- Documentation/virtual/kvm/mmu.txt | 8 ++++++++ arch/x86/include/asm/kvm_host.h | 5 +++++ 2 files changed, 13 insertions(+) diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt index ce6df51..5a6b2e2 100644 --- a/Documentation/virtual/kvm/mmu.txt +++ b/Documentation/virtual/kvm/mmu.txt @@ -214,6 +214,14 @@ Shadow pages contain the following information: It is only used on 32bit host which helps us to detect whether updating the 64bit spte is complete so that we can avoid reading the truncated value out of mmu-lock. + write_flooding_count: + In order to sync the page table between guest and host, the page sometimes + needs to be write-protected (see "Synchronized and unsynchronized pages" + below), any write to the page can cause write emulation. If the emulation + on the page is too frequent we'd better unmap the page to avoid the + future emulation. write_flooding_count aims at this optimization which is + increased when the page needs to be write emulated and cleared when the + page is actually used. Reverse map =========== diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 1dac2c1..5eb5382 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -234,6 +234,11 @@ struct kvm_mmu_page { int clear_spte_count; #endif + /* + * Increased when the page needs to be write emulated, cleared + * when the page is actually used as page table to avoid frequent + * emulation on the page. + */ int write_flooding_count; }; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/