From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753726AbaHNHG3 (ORCPT ); Thu, 14 Aug 2014 03:06:29 -0400 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:46719 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751832AbaHNHG1 (ORCPT ); Thu, 14 Aug 2014 03:06:27 -0400 Message-ID: <53EC5FE7.6040904@linux.vnet.ibm.com> Date: Thu, 14 Aug 2014 15:06:15 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: gleb@kernel.org CC: avi.kivity@gmail.com, mtosatti@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, stable@vger.kernel.org, David Matlack Subject: Re: [PATCH 1/2] KVM: fix cache stale memslot info with correct mmio generation number References: <1407999713-3726-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> In-Reply-To: <1407999713-3726-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14081407-2000-0000-0000-0000018806FF Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sorry, the title is not clear enough. This is the v2 which fixes the issue pointed out by David: " the generation number actually decreases." Please review. On 08/14/2014 03:01 PM, Xiao Guangrong wrote: > We may cache the current mmio generation number and stale memslot info > into spte, like this scenarioļ¼š > > CPU 0 CPU 1 > page fault: add a new memslot > read memslot and detecting its a mmio access > update memslots > update generation number > read generation number > cache the gpa and current gen number into spte > > So, if guest accesses the gpa later, it will generate a incorrect > mmio exit > > This patch fixes it by updating the generation number after > synchronize_srcu_expedited() that makes sure the generation > number updated only if memslots update is finished > > Cc: stable@vger.kernel.org > Cc: David Matlack > Signed-off-by: Xiao Guangrong > --- > virt/kvm/kvm_main.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 33712fb..bb40df3 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -96,7 +96,7 @@ static void hardware_disable_all(void); > > static void kvm_io_bus_destroy(struct kvm_io_bus *bus); > static void update_memslots(struct kvm_memslots *slots, > - struct kvm_memory_slot *new, u64 last_generation); > + struct kvm_memory_slot *new); > > static void kvm_release_pfn_dirty(pfn_t pfn); > static void mark_page_dirty_in_slot(struct kvm *kvm, > @@ -687,8 +687,7 @@ static void sort_memslots(struct kvm_memslots *slots) > } > > static void update_memslots(struct kvm_memslots *slots, > - struct kvm_memory_slot *new, > - u64 last_generation) > + struct kvm_memory_slot *new) > { > if (new) { > int id = new->id; > @@ -699,8 +698,6 @@ static void update_memslots(struct kvm_memslots *slots, > if (new->npages != npages) > sort_memslots(slots); > } > - > - slots->generation = last_generation + 1; > } > > static int check_memory_region_flags(struct kvm_userspace_memory_region *mem) > @@ -722,9 +719,12 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm, > { > struct kvm_memslots *old_memslots = kvm->memslots; > > - update_memslots(slots, new, kvm->memslots->generation); > + /* ensure generation number is always increased. */ > + slots->generation = old_memslots->generation; > + update_memslots(slots, new); > rcu_assign_pointer(kvm->memslots, slots); > synchronize_srcu_expedited(&kvm->srcu); > + slots->generation++; > > kvm_arch_memslots_updated(kvm); >