From patchwork Thu Nov 4 11:56:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Li RongQing X-Patchwork-Id: 12602951 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DF96C433EF for ; Thu, 4 Nov 2021 11:56:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36902611EF for ; Thu, 4 Nov 2021 11:56:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230148AbhKDL65 (ORCPT ); Thu, 4 Nov 2021 07:58:57 -0400 Received: from mx417.baidu.com ([124.64.200.157]:1797 "EHLO mx421.baidu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S229505AbhKDL6z (ORCPT ); Thu, 4 Nov 2021 07:58:55 -0400 Received: from bjhw-sys-rpm015653cc5.bjhw.baidu.com (bjhw-sys-rpm015653cc5.bjhw.baidu.com [10.227.53.39]) by mx421.baidu.com (Postfix) with ESMTP id 106452F0055D; Thu, 4 Nov 2021 19:56:15 +0800 (CST) Received: from localhost (localhost [127.0.0.1]) by bjhw-sys-rpm015653cc5.bjhw.baidu.com (Postfix) with ESMTP id EAB83D9933; Thu, 4 Nov 2021 19:56:14 +0800 (CST) From: Li RongQing To: kvm@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, lirongqing@baidu.com, stable@kernel.org Subject: [v4][PATCH 2/2] KVM: Clear pv eoi pending bit only when it is set Date: Thu, 4 Nov 2021 19:56:14 +0800 Message-Id: <1636026974-50555-2-git-send-email-lirongqing@baidu.com> X-Mailer: git-send-email 1.7.1 In-Reply-To: <1636026974-50555-1-git-send-email-lirongqing@baidu.com> References: <1636026974-50555-1-git-send-email-lirongqing@baidu.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org merge pv_eoi_get_pending and pv_eoi_clr_pending into a single function pv_eoi_test_and_clear_pending, which returns and clear the value of the pending bit. and clear pv eoi pending bit only when it is set, to avoid calling pv_eoi_put_user(), this can speed about 300 nsec on AMD EPYC most of the time Suggested-by: Vitaly Kuznetsov Suggested-by: Paolo Bonzini Signed-off-by: Li RongQing Reviewed-by: Vitaly Kuznetsov diff v2: merge as pv_eoi_test_and_clear_pending diff v3: remove printk in a new patch diff v4: fix comments place arch/x86/kvm/lapic.c | 40 +++++++++++++++++++--------------------- 1 files changed, 19 insertions(+), 21 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 752c48e..b1de23e 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -673,15 +673,6 @@ static inline bool pv_eoi_enabled(struct kvm_vcpu *vcpu) return vcpu->arch.pv_eoi.msr_val & KVM_MSR_ENABLED; } -static bool pv_eoi_get_pending(struct kvm_vcpu *vcpu) -{ - u8 val; - if (pv_eoi_get_user(vcpu, &val) < 0) - return false; - - return val & KVM_PV_EOI_ENABLED; -} - static void pv_eoi_set_pending(struct kvm_vcpu *vcpu) { if (pv_eoi_put_user(vcpu, KVM_PV_EOI_ENABLED) < 0) @@ -690,12 +681,26 @@ static void pv_eoi_set_pending(struct kvm_vcpu *vcpu) __set_bit(KVM_APIC_PV_EOI_PENDING, &vcpu->arch.apic_attention); } -static void pv_eoi_clr_pending(struct kvm_vcpu *vcpu) +static bool pv_eoi_test_and_clr_pending(struct kvm_vcpu *vcpu) { - if (pv_eoi_put_user(vcpu, KVM_PV_EOI_DISABLED) < 0) - return; + u8 val; + + if (pv_eoi_get_user(vcpu, &val) < 0) + return false; + + val &= KVM_PV_EOI_ENABLED; + + if (val && pv_eoi_put_user(vcpu, KVM_PV_EOI_DISABLED) < 0) + return false; + /* + * Clear pending bit in any case: it will be set again on vmentry. + * While this might not be ideal from performance point of view, + * this makes sure pv eoi is only enabled when we know it's safe. + */ __clear_bit(KVM_APIC_PV_EOI_PENDING, &vcpu->arch.apic_attention); + + return val; } static int apic_has_interrupt_for_ppr(struct kvm_lapic *apic, u32 ppr) @@ -2671,7 +2676,6 @@ void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu) static void apic_sync_pv_eoi_from_guest(struct kvm_vcpu *vcpu, struct kvm_lapic *apic) { - bool pending; int vector; /* * PV EOI state is derived from KVM_APIC_PV_EOI_PENDING in host @@ -2685,14 +2689,8 @@ static void apic_sync_pv_eoi_from_guest(struct kvm_vcpu *vcpu, * -> host enabled PV EOI, guest executed EOI. */ BUG_ON(!pv_eoi_enabled(vcpu)); - pending = pv_eoi_get_pending(vcpu); - /* - * Clear pending bit in any case: it will be set again on vmentry. - * While this might not be ideal from performance point of view, - * this makes sure pv eoi is only enabled when we know it's safe. - */ - pv_eoi_clr_pending(vcpu); - if (pending) + + if (pv_eoi_test_and_clr_pending(vcpu)) return; vector = apic_set_eoi(apic); trace_kvm_pv_eoi(apic, vector);