Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934114Ab3CSHgy (ORCPT ); Tue, 19 Mar 2013 03:36:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:13797 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933042Ab3CSHgw (ORCPT ); Tue, 19 Mar 2013 03:36:52 -0400 Date: Tue, 19 Mar 2013 09:36:48 +0200 From: Gleb Natapov To: Xiao Guangrong Cc: Eric Northup , Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH 5/5] KVM: MMU: fast invalid all mmio sptes Message-ID: <20130319073648.GT11223@redhat.com> References: <51433D98.4050605@linux.vnet.ibm.com> <51433E71.2070107@linux.vnet.ibm.com> <5147D858.4010805@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5147D858.4010805@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3026 Lines: 67 On Tue, Mar 19, 2013 at 11:15:36AM +0800, Xiao Guangrong wrote: > On 03/19/2013 06:16 AM, Eric Northup wrote: > > On Fri, Mar 15, 2013 at 8:29 AM, Xiao Guangrong > > wrote: > >> This patch tries to introduce a very simple and scale way to invalid all > >> mmio sptes - it need not walk any shadow pages and hold mmu-lock > >> > >> KVM maintains a global mmio invalid generation-number which is stored in > >> kvm->arch.mmio_invalid_gen and every mmio spte stores the current global > >> generation-number into his available bits when it is created > >> > >> When KVM need zap all mmio sptes, it just simply increase the global > >> generation-number. When guests do mmio access, KVM intercepts a MMIO #PF > >> then it walks the shadow page table and get the mmio spte. If the > >> generation-number on the spte does not equal the global generation-number, > >> it will go to the normal #PF handler to update the mmio spte > >> > >> Since 19 bits are used to store generation-number on mmio spte, the > >> generation-number can be round after 33554432 times. It is large enough > >> for nearly all most cases, but making the code be more strong, we zap all > >> shadow pages when the number is round > >> > >> Signed-off-by: Xiao Guangrong > >> --- > >> arch/x86/include/asm/kvm_host.h | 2 + > >> arch/x86/kvm/mmu.c | 61 +++++++++++++++++++++++++++++++++------ > >> arch/x86/kvm/mmutrace.h | 17 +++++++++++ > >> arch/x86/kvm/paging_tmpl.h | 7 +++- > >> arch/x86/kvm/vmx.c | 4 ++ > >> arch/x86/kvm/x86.c | 6 +-- > >> 6 files changed, 82 insertions(+), 15 deletions(-) > >> > >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > >> index ef7f4a5..572398e 100644 > >> --- a/arch/x86/include/asm/kvm_host.h > >> +++ b/arch/x86/include/asm/kvm_host.h > >> @@ -529,6 +529,7 @@ struct kvm_arch { > >> unsigned int n_requested_mmu_pages; > >> unsigned int n_max_mmu_pages; > >> unsigned int indirect_shadow_pages; > >> + unsigned int mmio_invalid_gen; > > > > Could this get initialized to something close to the wrap-around > > value, so that the wrap-around case gets more real-world coverage? > > I am afraid we can not. We cache the current mmio_invalid_gen into mmio spte when > it is created no matter what the initiation value is. > > If you have a better way, please show me. ;) > The idea is to initialize mmio_invalid_gen to value close to MAX_GEN in order to exercise + if (unlikely(kvm->arch.mmio_invalid_gen++ == MAX_GEN)) { + kvm->arch.mmio_invalid_gen = 0; + return kvm_mmu_zap_all(kvm); + } path more often. -- Gleb. -- 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/