From patchwork Sat Oct 9 02:12:32 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 12546945 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 1C325C433FE for ; Sat, 9 Oct 2021 02:17:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0501E60F57 for ; Sat, 9 Oct 2021 02:17:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244751AbhJICTH (ORCPT ); Fri, 8 Oct 2021 22:19:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244317AbhJICSb (ORCPT ); Fri, 8 Oct 2021 22:18:31 -0400 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D7D9C0612DE for ; Fri, 8 Oct 2021 19:14:18 -0700 (PDT) Received: by mail-qv1-xf49.google.com with SMTP id hf12-20020a0562140e8c00b00382cdfe644eso10292694qvb.23 for ; Fri, 08 Oct 2021 19:14:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=reply-to:date:in-reply-to:message-id:mime-version:references :subject:from:to:cc; bh=60FaGe3jHfzi2vANN4FyfF/i5oEKd4JaFx8/SVEFBNk=; b=Z1P8991nqO/keHHcPNDLRVMsJotsLW7zCMS8prAeIixKQ9mUd7DFllwUbuaHgVSrWZ FkvVrJgBJx0hc4CnzRBKZSR1hitB3Pk7jqHRDt0WmtqyCKKVVvm7gD0Q9FoIUaVCRIyp YiCXIJxWnPrhfp4kvu9z8/hF1gQOGdE7O7cz6QeTcYuVmieoH7ELJCd7UMv/HDJr1lHI JdSdjZZTm0cDCLqT8cUYvWrMLcAK8JU652nI2ulS+DYSnd22rQAqVDPjiZw3qVcCjDi0 GqTi9TAncXe+Iuc9CVjDDeSGYGD369tFbR8wEt1kGo66QnpkLVtv3NIEb5UQVw6604Ie 3W8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:reply-to:date:in-reply-to:message-id :mime-version:references:subject:from:to:cc; bh=60FaGe3jHfzi2vANN4FyfF/i5oEKd4JaFx8/SVEFBNk=; b=bUDbMEisJl5Z87fYENf05RORjmH3WZW+9CzqCFq9D6X42qrBYkx3Rt5qrI8FmRFIig f89xeqUEx0qVAOr9s0knayS23Xkbm0Q0xtnXxyTYLVIHCYVXAYoGUmzcqo6nwR0UGsW7 hXg+jV2KTpWJLiflOGu+Eghc3nuZl48bYgvJgQpXybrqISaIz63GSxflXbhGRPwnoILt 3D2jtTkR7AdqrhHUc3bmxZVzxdFie6rXFcwDjbu3XeqfdESy/mJtcbassyqhpT7qyQ5b b1ps9B1C1OkqkEg5uKWgObcSfMvgTSCGwAPoDnAP0fiT7QpX7qwJhC2LJ/XnkLKMkao8 ojkA== X-Gm-Message-State: AOAM530WA2v9MkmAhIT9JF81lM0CevD+RsYPjh1+w00Nirn8woBjxIrR Q3WD6XGf7CtHbmbeTBre9kJIUJ+rgKI= X-Google-Smtp-Source: ABdhPJzz4hkmJ133tsw9efdKVMZh6wi7X37BBmBb9YEFsyE1x8BdZiU7lUBQl0qiUIYV4wWlbCGAte9NXc4= X-Received: from seanjc798194.pdx.corp.google.com ([2620:15c:90:200:e39b:6333:b001:cb]) (user=seanjc job=sendgmr) by 2002:ac8:42da:: with SMTP id g26mr1839130qtm.368.1633745657436; Fri, 08 Oct 2021 19:14:17 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 8 Oct 2021 19:12:32 -0700 In-Reply-To: <20211009021236.4122790-1-seanjc@google.com> Message-Id: <20211009021236.4122790-40-seanjc@google.com> Mime-Version: 1.0 References: <20211009021236.4122790-1-seanjc@google.com> X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v2 39/43] KVM: VMX: Don't do full kick when triggering posted interrupt "fails" From: Sean Christopherson To: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Paolo Bonzini Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Replace the full "kick" with just the "wake" in the fallback path when triggering a virtual interrupt via a posted interrupt fails because the guest is not IN_GUEST_MODE. If the guest transitions into guest mode between the check and the kick, then it's guaranteed to see the pending interrupt as KVM syncs the PIR to IRR (and onto GUEST_RVI) after setting IN_GUEST_MODE. Kicking the guest in this case is nothing more than an unnecessary VM-Exit (and host IRQ). Opportunistically update comments to explain the various ordering rules and barriers at play. Signed-off-by: Sean Christopherson --- arch/x86/kvm/vmx/vmx.c | 16 ++++++++++++++-- arch/x86/kvm/x86.c | 5 +++-- 2 files changed, 17 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 13e732a818f3..44d760dde0f9 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3978,10 +3978,16 @@ static int vmx_deliver_nested_posted_interrupt(struct kvm_vcpu *vcpu, * we will accomplish it in the next vmentry. */ vmx->nested.pi_pending = true; + /* + * The smp_wmb() in kvm_make_request() pairs with the smp_mb_*() + * after setting vcpu->mode in vcpu_enter_guest(), thus the vCPU + * is guaranteed to see the event request if triggering a posted + * interrupt "fails" because vcpu->mode != IN_GUEST_MODE. + */ kvm_make_request(KVM_REQ_EVENT, vcpu); /* the PIR and ON have been set by L1. */ if (!kvm_vcpu_trigger_posted_interrupt(vcpu, true)) - kvm_vcpu_kick(vcpu); + kvm_vcpu_wake_up(vcpu); return 0; } return -1; @@ -4012,9 +4018,15 @@ static int vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu, int vector) if (pi_test_and_set_on(&vmx->pi_desc)) return 0; + /* + * The implied barrier in pi_test_and_set_on() pairs with the smp_mb_*() + * after setting vcpu->mode in vcpu_enter_guest(), thus the vCPU is + * guaranteed to see PID.ON=1 and sync the PIR to IRR if triggering a + * posted interrupt "fails" because vcpu->mode != IN_GUEST_MODE. + */ if (vcpu != kvm_get_running_vcpu() && !kvm_vcpu_trigger_posted_interrupt(vcpu, false)) - kvm_vcpu_kick(vcpu); + kvm_vcpu_wake_up(vcpu); return 0; } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9643f23c28c7..274d295cabfb 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9752,8 +9752,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) smp_mb__after_srcu_read_unlock(); /* - * This handles the case where a posted interrupt was - * notified with kvm_vcpu_kick. + * Process pending posted interrupts to handle the case where the + * notification IRQ arrived in the host, or was never sent (because the + * target vCPU wasn't running). */ if (kvm_lapic_enabled(vcpu) && vcpu->arch.apicv_active) static_call(kvm_x86_sync_pir_to_irr)(vcpu);