Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751929Ab0F1JvH (ORCPT ); Mon, 28 Jun 2010 05:51:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43652 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751348Ab0F1JvB (ORCPT ); Mon, 28 Jun 2010 05:51:01 -0400 Message-ID: <4C287081.40300@redhat.com> Date: Mon, 28 Jun 2010 12:50:57 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-3.fc13 Thunderbird/3.0.4 MIME-Version: 1.0 To: Xiao Guangrong CC: Marcelo Tosatti , LKML , KVM list Subject: Re: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted References: <4C2498EC.2010006@cn.fujitsu.com> <4C249BAD.6000609@cn.fujitsu.com> In-Reply-To: <4C249BAD.6000609@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2465 Lines: 69 On 06/25/2010 03:06 PM, Xiao Guangrong wrote: > Consider using small page to fit guest's large page mapping: > > If the mapping is writable but the dirty flag is not set, we will find > the read-only direct sp and setup the mapping, then if the write #PF > occur, we will mark this mapping writable in the read-only direct sp, > now, other real read-only mapping will happily write it without #PF. > > It may hurt guest's COW > > Fixed by re-install the mapping when write #PF occur. > > Signed-off-by: Xiao Guangrong > --- > arch/x86/kvm/mmu.c | 3 ++- > arch/x86/kvm/paging_tmpl.h | 18 ++++++++++++++++++ > 2 files changed, 20 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 556a798..0412ba4 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -153,7 +153,8 @@ module_param(oos_shadow, bool, 0644); > #define CREATE_TRACE_POINTS > #include "mmutrace.h" > > -#define SPTE_HOST_WRITEABLE (1ULL<< PT_FIRST_AVAIL_BITS_SHIFT) > +#define SPTE_HOST_WRITEABLE (1ULL<< PT_FIRST_AVAIL_BITS_SHIFT) > +#define SPTE_NO_DIRTY (2ULL<< PT_FIRST_AVAIL_BITS_SHIFT) > > #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level) > > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h > index e46eb8a..fdba751 100644 > --- a/arch/x86/kvm/paging_tmpl.h > +++ b/arch/x86/kvm/paging_tmpl.h > @@ -325,6 +325,20 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, > break; > } > > + if (*sptep& SPTE_NO_DIRTY) { > + struct kvm_mmu_page *child; > + > + WARN_ON(level != gw->level); > + WARN_ON(!is_shadow_present_pte(*sptep)); > + if (dirty) { > + child = page_header(*sptep& > + PT64_BASE_ADDR_MASK); > + mmu_page_remove_parent_pte(child, sptep); > + __set_spte(sptep, shadow_trap_nonpresent_pte); > + kvm_flush_remote_tlbs(vcpu->kvm); > + } > + } > + > Instead of adding a new bit, can you encode the protection in the direct sp's access bits? So we'll have one sp for read-only or writeable-but-not-dirty small pages, and another sp for writeable-and-dirty small pages. -- error compiling committee.c: too many arguments to function -- 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/