From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 2/2] KVM: MMU: optimize pte write path if don't have protected sp Date: Tue, 05 Apr 2011 11:34:43 +0300 Message-ID: <4D9AD423.6060503@redhat.com> References: <4D8FF287.1040300@cn.fujitsu.com> <4D8FF2D2.9070109@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM To: Xiao Guangrong Return-path: In-Reply-To: <4D8FF2D2.9070109@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 03/28/2011 04:30 AM, Xiao Guangrong wrote: > Simplely return from kvm_mmu_pte_write path if no shadow page is > write-protected, than we can avoid to walk all shadow pages and hold > mmu-lock > > Signed-off-by: Xiao Guangrong > --- > arch/x86/kvm/mmu.c | 8 ++++++++ > 1 files changed, 8 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 2841805..ccac6c4 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -3219,6 +3219,11 @@ static void kvm_mmu_access_page(struct kvm_vcpu *vcpu, gfn_t gfn) > set_bit(PT_ACCESSED_SHIFT, (unsigned long *)spte); > } > > +static bool need_track_pte_changed(struct kvm_vcpu *vcpu) > +{ > + return !tdp_enabled || mmu_is_nested(vcpu); > +} > + What happens if this vcpu is nested but another vcpu is not? Or if we have some indirect pages, but currently we're in non-nested mode? Suggest instead to keep track of the number of indirect pages across the guest. If it's zero, we can exit early. > void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, > const u8 *new, int bytes, > bool guest_initiated) > @@ -3233,6 +3238,9 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, > int level, npte, invlpg_counter, r, flooded = 0; > bool remote_flush, local_flush, zap_page; > > + if (!need_track_pte_changed(vcpu)) > + return; > + > zap_page = remote_flush = local_flush = false; > offset = offset_in_page(gpa); > -- error compiling committee.c: too many arguments to function