Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755156Ab0GCKfX (ORCPT ); Sat, 3 Jul 2010 06:35:23 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:60912 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754844Ab0GCKfV (ORCPT ); Sat, 3 Jul 2010 06:35:21 -0400 Message-ID: <4C2F117C.2000006@cn.fujitsu.com> Date: Sat, 03 Jul 2010 18:31:24 +0800 From: Xiao Guangrong User-Agent: Thunderbird 2.0.0.24 (Windows/20100228) MIME-Version: 1.0 To: Marcelo Tosatti CC: Avi Kivity , LKML , KVM list Subject: Re: [PATCH v4 5/6] KVM: MMU: combine guest pte read between walk and pte prefetch References: <4C2C9DC0.8050607@cn.fujitsu.com> <4C2C9E6C.2040803@cn.fujitsu.com> <20100702170303.GC25969@amt.cnet> In-Reply-To: <20100702170303.GC25969@amt.cnet> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4222 Lines: 135 Marcelo Tosatti wrote: > On Thu, Jul 01, 2010 at 09:55:56PM +0800, Xiao Guangrong wrote: >> Combine guest pte read between guest pte walk and pte prefetch >> >> Signed-off-by: Xiao Guangrong >> --- >> arch/x86/kvm/paging_tmpl.h | 48 ++++++++++++++++++++++++++++++------------- >> 1 files changed, 33 insertions(+), 15 deletions(-) > > Can't do this, it can miss invlpg: > > vcpu0 vcpu1 > read guest ptes > modify guest pte > invlpg > instantiate stale > guest pte Ah, oops, sorry :-( > > See how the pte is reread inside fetch with mmu_lock held. > It looks like something is broken in 'fetch' functions, this patch will fix it. Subject: [PATCH] KVM: MMU: fix last level broken in FNAME(fetch) We read the guest level out of 'mmu_lock', sometimes, the host mapping is confusion. Consider this case: VCPU0: VCPU1 Read guest mapping, assume the mapping is: GLV3 -> GLV2 -> GLV1 -> GFNA, And in the host, the corresponding mapping is HLV3 -> HLV2 -> HLV1(P=0) Write GLV1 and cause the mapping point to GFNB (May occur in pte_write or invlpg path) Mapping GLV1 to GFNA This issue only occurs in the last indirect mapping, since if the middle mapping is changed, the mapping will be zapped, then it will be detected in the FNAME(fetch) path, but when it map the last level, it not checked. Fixed by also check the last level. Signed-off-by: Xiao Guangrong --- arch/x86/kvm/paging_tmpl.h | 32 +++++++++++++++++++++++++------- 1 files changed, 25 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 3350c02..e617e93 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -291,6 +291,20 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, gpte_to_gfn(gpte), pfn, true, true); } +static bool FNAME(check_level_mapping)(struct kvm_vcpu *vcpu, + struct guest_walker *gw, int level) +{ + pt_element_t curr_pte; + int r; + + r = kvm_read_guest_atomic(vcpu->kvm, gw->pte_gpa[level - 1], + &curr_pte, sizeof(curr_pte)); + if (r || curr_pte != gw->ptes[level - 1]) + return false; + + return true; +} + /* * Fetch a shadow pte for a specific level in the paging hierarchy. */ @@ -304,11 +318,9 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, u64 spte, *sptep = NULL; int direct; gfn_t table_gfn; - int r; int level; - bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]); + bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]), check = true; unsigned direct_access; - pt_element_t curr_pte; struct kvm_shadow_walk_iterator iterator; if (!is_present_gpte(gw->ptes[gw->level - 1])) @@ -322,6 +334,12 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, level = iterator.level; sptep = iterator.sptep; if (iterator.level == hlevel) { + if (check && level == gw->level && + !FNAME(check_level_mapping)(vcpu, gw, hlevel)) { + kvm_release_pfn_clean(pfn); + break; + } + mmu_set_spte(vcpu, sptep, access, gw->pte_access & access, user_fault, write_fault, @@ -376,10 +394,10 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, sp = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1, direct, access, sptep); if (!direct) { - r = kvm_read_guest_atomic(vcpu->kvm, - gw->pte_gpa[level - 2], - &curr_pte, sizeof(curr_pte)); - if (r || curr_pte != gw->ptes[level - 2]) { + if (hlevel == level - 1) + check = false; + + if (!FNAME(check_level_mapping)(vcpu, gw, level - 1)) { kvm_mmu_put_page(sp, sptep); kvm_release_pfn_clean(pfn); sptep = NULL; -- 1.6.1.2 -- 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/