From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753279AbdKIKyL (ORCPT ); Thu, 9 Nov 2017 05:54:11 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46778 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752838AbdKIKyI (ORCPT ); Thu, 9 Nov 2017 05:54:08 -0500 Subject: Re: [PATCH RESEND 3/3] KVM: Add flush_on_enter before guest enter To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li References: <1510192934-5369-1-git-send-email-wanpeng.li@hotmail.com> <1510192934-5369-4-git-send-email-wanpeng.li@hotmail.com> From: Paolo Bonzini Message-ID: Date: Thu, 9 Nov 2017 11:54:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1510192934-5369-4-git-send-email-wanpeng.li@hotmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Thu, 09 Nov 2017 10:54:08 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/11/2017 03:02, Wanpeng Li wrote: > From: Wanpeng Li > > PV-Flush guest would indicate to flush on enter, flush the TLB before > entering and exiting the guest. > > Cc: Paolo Bonzini > Cc: Radim Krčmář > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/x86.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 1ea28a2..f295360 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2116,7 +2116,13 @@ static void record_steal_time(struct kvm_vcpu *vcpu) > &vcpu->arch.st.steal, sizeof(struct kvm_steal_time)))) > return; > > - vcpu->arch.st.steal.preempted = KVM_VCPU_NOT_PREEMPTED; > + if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_NOT_PREEMPTED) == > + (KVM_VCPU_SHOULD_FLUSH | KVM_VCPU_PREEMPTED)) > + /* > + * Do TLB_FLUSH before entering the guest, its passed > + * the stage of request checking > + */ > + kvm_x86_ops->tlb_flush(vcpu); > > if (vcpu->arch.st.steal.version & 1) > vcpu->arch.st.steal.version += 1; /* first time write, random junk */ > @@ -2887,7 +2893,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu) > if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED)) > return; > > - vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED; > + if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_PREEMPTED) == > + KVM_VCPU_SHOULD_FLUSH) > + kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu); This is not necessary. Instead, you can just OR the KVM_VCPU_PREEMPTED bit; record_steal_time will pick up the request and do the TLB flush later. Also, I think this is a case where you should prefer INVVPID to INVEP. That's because "execution of the INVEPT instruction invalidates guest-physical mappings and combined mappings" while "execution of the INVVPID instruction invalidates linear mappings and combined mappings". In this case, invalidating guest-physical mapping is unnecessary. So you could add a new bool argument to kvm_x86_ops->tlb_flush. In vmx.c, __vmx_flush_tlb can do invept if "enable_ept && (invalidate_gpa || !enable_vpid)". If !enable_ept && !enable_vpid, the feature cannot be made available. Thanks, Paolo > kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime, > &vcpu->arch.st.steal.preempted, >