From patchwork Tue Jan 25 11:59:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wanpeng Li X-Patchwork-Id: 12723712 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E71F3C433EF for ; Tue, 25 Jan 2022 12:04:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1391989AbiAYMEf (ORCPT ); Tue, 25 Jan 2022 07:04:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1382757AbiAYMAo (ORCPT ); Tue, 25 Jan 2022 07:00:44 -0500 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3DBB3C06173B; Tue, 25 Jan 2022 04:00:30 -0800 (PST) Received: by mail-pj1-x102d.google.com with SMTP id w12-20020a17090a528c00b001b276aa3aabso1911538pjh.0; Tue, 25 Jan 2022 04:00:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id; bh=Z2eSIKO2hPoT+F0EzCBQkbD8++MWEeeyBWhA5iN+68Y=; b=ALI7ZgAa3oPCEuVPuONBKC63VKdQnQJeEy7qFRK699JkPvR7gWOFbzGjLsglzuYD52 2yHA3r92N2bIK0ZksZD8njL5BAlHHcNCheGp1PHn+D1fVjO76qBpFlTNfLnUv/DlR7DW AO2VFW08Twc34e8cqgQS/gaYEmzYtu2iaW6IVT/QEfqVPibZoSv/2zt8U8wwCsqJuEAH 1M2Vl5l55ywHvBrjbwXyTAM1idFUjbWRv+K5t5Tz/yk+mObHo5H3zy6OG02HLn9MUZsS T7MCeAg5A30xSfp9RtGu0u+EoShs6bZ6VVL7rvBi6YfpwnJ7BGb+qeovwbebc1cVJICc vE2w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=Z2eSIKO2hPoT+F0EzCBQkbD8++MWEeeyBWhA5iN+68Y=; b=sfFITQCQSJDzN0Sq3ap2cHgQGRfVa1SXUSIB9o26LwUsDPGE1f81dRli186yl3jtU7 E/tg3kx9rZo48Q+pELESi+WplbsRK5AmnjOtF7IE7TVGoQuQNOYdbLZQ02Wav1iYCFND qy9HXsZh8F5HeQkDZg+dcAE/stGR6qIC4OdSwFEBnYYCcfW6/j7SRWXX6Swa2m4rNBsi hDF2hXux+QwIcltL36eu0t5BpsN1JVKFQshdaaPLagCFx4iirFmYHaw3ofBDoj1y33SD mnGi6BcoeXQw0e6MxMNU8GkNbs2L9LWCECR1kZMRW5kx5XHhztMjoLSYaUfeQYBfRgYi 9gzQ== X-Gm-Message-State: AOAM531ZIVAp1gjlCBeSEHd6gAazQ3KIHWB5BVIgawcHNEiV+HDnLl0s ypRGLMm0ma8R2RWLnzdlgODJ+VhPlwoAsQ== X-Google-Smtp-Source: ABdhPJxboyPEW0uwim9wsTVOxgUlkUtCTkh+LyP78FY20vNjpwPE1Uw/P3LJf5XOzjr/65Rvwj6LJQ== X-Received: by 2002:a17:90a:de08:: with SMTP id m8mr3209326pjv.102.1643112029424; Tue, 25 Jan 2022 04:00:29 -0800 (PST) Received: from localhost.localdomain ([203.205.141.110]) by smtp.googlemail.com with ESMTPSA id ga21sm2566108pjb.2.2022.01.25.04.00.27 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Jan 2022 04:00:29 -0800 (PST) From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: [PATCH RESEND v2] KVM: VMX: Dont' send posted IRQ if vCPU == this vCPU and vCPU is IN_GUEST_MODE Date: Tue, 25 Jan 2022 03:59:39 -0800 Message-Id: <1643111979-36447-1-git-send-email-wanpengli@tencent.com> X-Mailer: git-send-email 2.7.4 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Wanpeng Li When delivering a virtual interrupt, don't actually send a posted interrupt if the target vCPU is also the currently running vCPU and is IN_GUEST_MODE, in which case the interrupt is being sent from a VM-Exit fastpath and the core run loop in vcpu_enter_guest() will manually move the interrupt from the PIR to vmcs.GUEST_RVI. IRQs are disabled while IN_GUEST_MODE, thus there's no possibility of the virtual interrupt being sent from anything other than KVM, i.e. KVM won't suppress a wake event from an IRQ handler (see commit fdba608f15e2, "KVM: VMX: Wake vCPU when delivering posted IRQ even if vCPU == this vCPU"). Eliding the posted interrupt restores the performance provided by the combination of commits 379a3c8ee444 ("KVM: VMX: Optimize posted-interrupt delivery for timer fastpath") and 26efe2fd92e5 ("KVM: VMX: Handle preemption timer fastpath"). Thanks Sean for better comments. Suggested-by: Chao Gao Reviewed-by: Sean Christopherson Signed-off-by: Wanpeng Li --- arch/x86/kvm/vmx/vmx.c | 40 +++++++++++++++++++++------------------- 1 file changed, 21 insertions(+), 19 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index fe06b02994e6..e06377c9a4cf 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3908,31 +3908,33 @@ static inline void kvm_vcpu_trigger_posted_interrupt(struct kvm_vcpu *vcpu, #ifdef CONFIG_SMP if (vcpu->mode == IN_GUEST_MODE) { /* - * The vector of interrupt to be delivered to vcpu had - * been set in PIR before this function. + * The vector of the virtual has already been set in the PIR. + * Send a notification event to deliver the virtual interrupt + * unless the vCPU is the currently running vCPU, i.e. the + * event is being sent from a fastpath VM-Exit handler, in + * which case the PIR will be synced to the vIRR before + * re-entering the guest. * - * Following cases will be reached in this block, and - * we always send a notification event in all cases as - * explained below. + * When the target is not the running vCPU, the following + * possibilities emerge: * - * Case 1: vcpu keeps in non-root mode. Sending a - * notification event posts the interrupt to vcpu. + * Case 1: vCPU stays in non-root mode. Sending a notification + * event posts the interrupt to the vCPU. * - * Case 2: vcpu exits to root mode and is still - * runnable. PIR will be synced to vIRR before the - * next vcpu entry. Sending a notification event in - * this case has no effect, as vcpu is not in root - * mode. + * Case 2: vCPU exits to root mode and is still runnable. The + * PIR will be synced to the vIRR before re-entering the guest. + * Sending a notification event is ok as the host IRQ handler + * will ignore the spurious event. * - * Case 3: vcpu exits to root mode and is blocked. - * vcpu_block() has already synced PIR to vIRR and - * never blocks vcpu if vIRR is not cleared. Therefore, - * a blocked vcpu here does not wait for any requested - * interrupts in PIR, and sending a notification event - * which has no effect is safe here. + * Case 3: vCPU exits to root mode and is blocked. vcpu_block() + * has already synced PIR to vIRR and never blocks the vCPU if + * the vIRR is not empty. Therefore, a blocked vCPU here does + * not wait for any requested interrupts in PIR, and sending a + * notification event also results in a benign, spurious event. */ - apic->send_IPI_mask(get_cpu_mask(vcpu->cpu), pi_vec); + if (vcpu != kvm_get_running_vcpu()) + apic->send_IPI_mask(get_cpu_mask(vcpu->cpu), pi_vec); return; } #endif