From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754385Ab3ETJTl (ORCPT ); Mon, 20 May 2013 05:19:41 -0400 Received: from e28smtp08.in.ibm.com ([122.248.162.8]:33078 "EHLO e28smtp08.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752925Ab3ETJTj (ORCPT ); Mon, 20 May 2013 05:19:39 -0400 Message-ID: <5199EA9E.3010909@linux.vnet.ibm.com> Date: Mon, 20 May 2013 17:19:26 +0800 From: Xiao Guangrong User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Gleb Natapov CC: avi.kivity@gmail.com, mtosatti@redhat.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v6 2/7] KVM: MMU: delete shadow page from hash list in kvm_mmu_prepare_zap_page References: <1368738782-18649-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <1368738782-18649-3-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <20130519104713.GE4725@redhat.com> In-Reply-To: <20130519104713.GE4725@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13052009-2000-0000-0000-00000C2DD4F7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/19/2013 06:47 PM, Gleb Natapov wrote: > On Fri, May 17, 2013 at 05:12:57AM +0800, Xiao Guangrong wrote: >> Move deletion shadow page from the hash list from kvm_mmu_commit_zap_page to >> kvm_mmu_prepare_zap_page so that we can call kvm_mmu_commit_zap_page >> once for multiple kvm_mmu_prepare_zap_page that can help us to avoid >> unnecessary TLB flush >> > Don't we call kvm_mmu_commit_zap_page() once for multiple > kvm_mmu_prepare_zap_page() now when possible? kvm_mmu_commit_zap_page() > gets a list as a parameter. I am not against the change, but wish to > understand it better. The changelong is not clear enough, i mean we can "call kvm_mmu_commit_zap_page once for multiple kvm_mmu_prepare_zap_page" when we use lock-break technique. If we do not do this, the page can be found in hashtable but they are linked on the invalid_list on other thread. > >> Signed-off-by: Xiao Guangrong >> --- >> arch/x86/kvm/mmu.c | 8 ++++++-- >> 1 files changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c >> index 40d7b2d..682ecb4 100644 >> --- a/arch/x86/kvm/mmu.c >> +++ b/arch/x86/kvm/mmu.c >> @@ -1466,7 +1466,7 @@ static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr) >> static void kvm_mmu_free_page(struct kvm_mmu_page *sp) >> { >> ASSERT(is_empty_shadow_page(sp->spt)); >> - hlist_del(&sp->hash_link); >> + >> list_del(&sp->link); >> free_page((unsigned long)sp->spt); >> if (!sp->role.direct) >> @@ -1655,7 +1655,8 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm, >> >> #define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn) \ >> for_each_gfn_sp(_kvm, _sp, _gfn) \ >> - if ((_sp)->role.direct || (_sp)->role.invalid) {} else >> + if ((_sp)->role.direct || \ >> + ((_sp)->role.invalid && WARN_ON(1))) {} else >> >> /* @sp->gfn should be write-protected at the call site */ >> static int __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, >> @@ -2074,6 +2075,9 @@ static int kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp, >> unaccount_shadowed(kvm, sp->gfn); >> if (sp->unsync) >> kvm_unlink_unsync_page(kvm, sp); >> + >> + hlist_del_init(&sp->hash_link); >> + > What about moving this inside if() bellow and making it hlist_del()? > Leave the page on the hash if root_count is non zero. > It's a good idea. will update.