From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933109AbYDQJV0 (ORCPT ); Thu, 17 Apr 2008 05:21:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760384AbYDQJLZ (ORCPT ); Thu, 17 Apr 2008 05:11:25 -0400 Received: from bzq-179-150-194.static.bezeqint.net ([212.179.150.194]:59088 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762875AbYDQJLF (ORCPT ); Thu, 17 Apr 2008 05:11:05 -0400 From: Avi Kivity To: kvm-devel@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org, Marcelo Tosatti Subject: [PATCH 24/45] KVM: MMU: prepopulate guest pages after write-protecting Date: Thu, 17 Apr 2008 12:10:29 +0300 Message-Id: <1208423450-29415-25-git-send-email-avi@qumranet.com> X-Mailer: git-send-email 1.5.5 In-Reply-To: <1208423450-29415-1-git-send-email-avi@qumranet.com> References: <1208423450-29415-1-git-send-email-avi@qumranet.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Marcelo Tosatti Zdenek reported a bug where a looping "dmsetup status" eventually hangs on SMP guests. The problem is that kvm_mmu_get_page() prepopulates the shadow MMU before write protecting the guest page tables. By doing so, it leaves a window open where the guest can mark a pte as present while the host has shadow cached such pte as "notrap". Accesses to such address will fault in the guest without the host having a chance to fix the situation. Fix by moving the write protection before the pte prefetch. Signed-off-by: Marcelo Tosatti Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 5c4c166..c89bf23 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -852,9 +852,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, sp->gfn = gfn; sp->role = role; hlist_add_head(&sp->hash_link, bucket); - vcpu->arch.mmu.prefetch_page(vcpu, sp); if (!metaphysical) rmap_write_protect(vcpu->kvm, gfn); + vcpu->arch.mmu.prefetch_page(vcpu, sp); return sp; } -- 1.5.5