From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8E713C433E1 for ; Sat, 22 Aug 2020 04:01:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 729FD20732 for ; Sat, 22 Aug 2020 04:01:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725912AbgHVEBQ (ORCPT ); Sat, 22 Aug 2020 00:01:16 -0400 Received: from mga17.intel.com ([192.55.52.151]:41402 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725300AbgHVEBQ (ORCPT ); Sat, 22 Aug 2020 00:01:16 -0400 IronPort-SDR: yUu/cx37u8efnEV/L08bDndAWiX+xQj219NXoVRS8CBOOpm1bZC7pNK4mGaVRURiRsmNtvwSwe oqT6Wm/8Asfg== X-IronPort-AV: E=McAfee;i="6000,8403,9720"; a="135742831" X-IronPort-AV: E=Sophos;i="5.76,339,1592895600"; d="scan'208";a="135742831" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Aug 2020 21:01:15 -0700 IronPort-SDR: az/BSV7RSyZiBINLupZ52ug5lb0TI9qqa2rKE/pCL8zqRRJ579VSDUbWOtN+3nvF/BVZOPCYbT zlOpPpkOZn0w== X-IronPort-AV: E=Sophos;i="5.76,339,1592895600"; d="scan'208";a="498728955" Received: from sjchrist-ice.jf.intel.com (HELO sjchrist-ice) ([10.54.31.34]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Aug 2020 21:01:15 -0700 Date: Fri, 21 Aug 2020 21:01:14 -0700 From: Sean Christopherson To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: Re: [PATCH] KVM: LAPIC: Don't kick vCPU which is injecting already-expired timer Message-ID: <20200822040114.GF4769@sjchrist-ice> References: <1598001454-11709-1-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1598001454-11709-1-git-send-email-wanpengli@tencent.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 21, 2020 at 05:17:34PM +0800, Wanpeng Li wrote: > From: Wanpeng Li > > The kick after setting KVM_REQ_PENDING_TIMER is used to handle the timer > fires on a different pCPU which vCPU is running on, we don't need this > kick when injecting already-expired timer, this kick is expensive since > memory barrier, rcu, preemption disable/enable operations. This patch > reduces the overhead by don't kick vCPU which is injecting already-expired > timer. This should also call out the VMX preemption timer case, which also passes from_timer_fn=false but doesn't need a kick because kvm_lapic_expired_hv_timer() is called from the target vCPU. > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/lapic.c | 2 +- > arch/x86/kvm/x86.c | 5 +++-- > arch/x86/kvm/x86.h | 2 +- > 3 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 248095a..5b5ae66 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -1642,7 +1642,7 @@ static void apic_timer_expired(struct kvm_lapic *apic, bool from_timer_fn) > } > > atomic_inc(&apic->lapic_timer.pending); > - kvm_set_pending_timer(vcpu); > + kvm_set_pending_timer(vcpu, from_timer_fn); My vote would be to open code kvm_set_pending_timer() here and drop the helper, i.e. kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu); if (from_timer_fn) kvm_vcpu_kick(vcpu); with that and an updated changelog: Reviewed-by: Sean Christopherson > } > > static void start_sw_tscdeadline(struct kvm_lapic *apic) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 599d732..2a45405 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1778,10 +1778,11 @@ static s64 get_kvmclock_base_ns(void) > } > #endif > > -void kvm_set_pending_timer(struct kvm_vcpu *vcpu) > +void kvm_set_pending_timer(struct kvm_vcpu *vcpu, bool should_kick) > { > kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu); > - kvm_vcpu_kick(vcpu); > + if (should_kick) > + kvm_vcpu_kick(vcpu); > } > > static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock) > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index 995ab69..0eaae9c 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -246,7 +246,7 @@ static inline bool kvm_vcpu_latch_init(struct kvm_vcpu *vcpu) > return is_smm(vcpu) || kvm_x86_ops.apic_init_signal_blocked(vcpu); > } > > -void kvm_set_pending_timer(struct kvm_vcpu *vcpu); > +void kvm_set_pending_timer(struct kvm_vcpu *vcpu, bool should_kick); > void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip); > > void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr); > -- > 2.7.4 >