From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754112Ab2KLXww (ORCPT ); Mon, 12 Nov 2012 18:52:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:63126 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753268Ab2KLXwu (ORCPT ); Mon, 12 Nov 2012 18:52:50 -0500 Date: Mon, 12 Nov 2012 21:12:23 -0200 From: Marcelo Tosatti To: Xiao Guangrong Cc: Avi Kivity , LKML , KVM Subject: Re: [PATCH 2/5] KVM: MMU: simplify mmu_set_spte Message-ID: <20121112231223.GC5798@amt.cnet> References: <5097AC70.1080904@linux.vnet.ibm.com> <5097ACA0.7080408@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5097ACA0.7080408@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 05, 2012 at 08:10:08PM +0800, Xiao Guangrong wrote: > In order to detecting spte remapping, we can simply check whether the > spte has already been pointing to the pfn even if the spte is not the > last spte for middle spte is pointing to the kernel pfn which can not > be mapped to userspace > > Also, update slot and stat.lpages iff the spte is not remapped > > Signed-off-by: Xiao Guangrong > --- > arch/x86/kvm/mmu.c | 40 +++++++++++++--------------------------- > 1 files changed, 13 insertions(+), 27 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 692ebb1..4ea731e 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -2420,8 +2420,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, > pfn_t pfn, bool speculative, > bool host_writable) > { > - int was_rmapped = 0; > - int rmap_count; > + bool was_rmapped = false; > > pgprintk("%s: spte %llx access %x write_fault %d" > " user_fault %d gfn %llx\n", > @@ -2429,25 +2428,13 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, > write_fault, user_fault, gfn); > > if (is_rmap_spte(*sptep)) { > - /* > - * If we overwrite a PTE page pointer with a 2MB PMD, unlink > - * the parent of the now unreachable PTE. > - */ > - if (level > PT_PAGE_TABLE_LEVEL && > - !is_large_pte(*sptep)) { > - struct kvm_mmu_page *child; > - u64 pte = *sptep; > + if (pfn != spte_to_pfn(*sptep)) { > + struct kvm_mmu_page *sp = page_header(__pa(sptep)); > > - child = page_header(pte & PT64_BASE_ADDR_MASK); > - drop_parent_pte(child, sptep); > - kvm_flush_remote_tlbs(vcpu->kvm); How come its safe to drop this case?