From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: [PATCH 2/3] KVM: MMU: Remove user access when allowing kernel access to gpte.w=0 page Date: Thu, 27 May 2010 14:50:05 +0300 Message-ID: <1274961006-19413-3-git-send-email-avi@redhat.com> References: <1274961006-19413-1-git-send-email-avi@redhat.com> Cc: kvm@vger.kernel.org To: Xiao Guangrong , Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22484 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759184Ab0E0LuM (ORCPT ); Thu, 27 May 2010 07:50:12 -0400 In-Reply-To: <1274961006-19413-1-git-send-email-avi@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: If cr0.wp=0, we have to allow the guest kernel access to a page with pte.w=0. We do that by setting spte.w=1, since the host cr0.wp must remain set so the host can write protect pages. Once we allow write access, we must remove user access otherwise we mistakenly allow the user to write the page. Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 39dd8d3..56f8c3c 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1894,6 +1894,9 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, spte |= PT_WRITABLE_MASK; + if (!tdp_enabled && !(pte_access & ACC_WRITE_MASK)) + spte &= ~PT_USER_MASK; + /* * Optimization: for pte sync, if spte was writable the hash * lookup is unnecessary (and expensive). Write protection -- 1.7.1