From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756630Ab0KVDlK (ORCPT ); Sun, 21 Nov 2010 22:41:10 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:51967 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1756363Ab0KVDlI (ORCPT ); Sun, 21 Nov 2010 22:41:08 -0500 Message-ID: <4CE9E74E.7070908@cn.fujitsu.com> Date: Mon, 22 Nov 2010 11:45:18 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.11) Gecko/20100713 Thunderbird/3.0.6 MIME-Version: 1.0 To: Marcelo Tosatti CC: Avi Kivity , KVM , LKML Subject: Re: [PATCH v3 6/6] KVM: MMU: delay flush all tlbs on sync_page path References: <4CE63CF4.80502@cn.fujitsu.com> <4CE63DE2.9050408@cn.fujitsu.com> <20101119161118.GB20279@amt.cnet> In-Reply-To: <20101119161118.GB20279@amt.cnet> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2010-11-22 11:41:21, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2010-11-22 11:41:21, Serialize complete at 2010-11-22 11:41:21 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/20/2010 12:11 AM, Marcelo Tosatti wrote: >> void kvm_flush_remote_tlbs(struct kvm *kvm) >> { >> + int dirty_count = atomic_read(&kvm->tlbs_dirty); >> + >> + smp_mb(); >> if (make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH)) >> ++kvm->stat.remote_tlb_flush; >> + atomic_sub(dirty_count, &kvm->tlbs_dirty); >> } > > This is racy because kvm_flush_remote_tlbs might be called without > mmu_lock protection. Sorry for my carelessness, it should be 'cmpxchg' here. > You could decrease the counter on > invalidate_page/invalidate_range_start only, I want to avoid a unnecessary tlbs flush, if tlbs have been flushed after sync_page, then we don't need flush tlbs on invalidate_page/ invalidate_range_start path. > these are not fast paths > anyway. > How about below patch? it just needs one atomic operation. --- arch/x86/kvm/paging_tmpl.h | 4 ++-- include/linux/kvm_host.h | 2 ++ virt/kvm/kvm_main.c | 7 ++++++- 3 files changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index dfb906f..e64192f 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -781,14 +781,14 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) gfn = gpte_to_gfn(gpte); if (FNAME(map_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) { - kvm_flush_remote_tlbs(vcpu->kvm); + vcpu->kvm->tlbs_dirty++; continue; } if (gfn != sp->gfns[i]) { drop_spte(vcpu->kvm, &sp->spt[i], shadow_trap_nonpresent_pte); - kvm_flush_remote_tlbs(vcpu->kvm); + vcpu->kvm->tlbs_dirty++; continue; } diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 4bd663d..dafd90e 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -249,6 +249,7 @@ struct kvm { struct mmu_notifier mmu_notifier; unsigned long mmu_notifier_seq; long mmu_notifier_count; + long tlbs_dirty; #endif }; @@ -377,6 +378,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu); void kvm_resched(struct kvm_vcpu *vcpu); void kvm_load_guest_fpu(struct kvm_vcpu *vcpu); void kvm_put_guest_fpu(struct kvm_vcpu *vcpu); + void kvm_flush_remote_tlbs(struct kvm *kvm); void kvm_reload_remote_mmus(struct kvm *kvm); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index fb93ff9..fe0a1a7 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -168,8 +168,12 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) void kvm_flush_remote_tlbs(struct kvm *kvm) { + long dirty_count = kvm->tlbs_dirty; + + smp_mb(); if (make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH)) ++kvm->stat.remote_tlb_flush; + cmpxchg(&kvm->tlbs_dirty, dirty_count, 0); } void kvm_reload_remote_mmus(struct kvm *kvm) @@ -249,7 +253,7 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn, idx = srcu_read_lock(&kvm->srcu); spin_lock(&kvm->mmu_lock); kvm->mmu_notifier_seq++; - need_tlb_flush = kvm_unmap_hva(kvm, address); + need_tlb_flush = kvm_unmap_hva(kvm, address) | kvm->tlbs_dirty; spin_unlock(&kvm->mmu_lock); srcu_read_unlock(&kvm->srcu, idx); @@ -293,6 +297,7 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, kvm->mmu_notifier_count++; for (; start < end; start += PAGE_SIZE) need_tlb_flush |= kvm_unmap_hva(kvm, start); + need_tlb_flush |= kvm->tlbs_dirty; spin_unlock(&kvm->mmu_lock); srcu_read_unlock(&kvm->srcu, idx); -- 1.7.0.4