From nobody Tue Apr 7 07:06:53 2026 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 9C1EFECAAD4 for ; Wed, 31 Aug 2022 00:37:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232084AbiHaAhU (ORCPT ); Tue, 30 Aug 2022 20:37:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231886AbiHaAgu (ORCPT ); Tue, 30 Aug 2022 20:36:50 -0400 Received: from mail-pl1-x649.google.com (mail-pl1-x649.google.com [IPv6:2607:f8b0:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C161FA6AD5 for ; Tue, 30 Aug 2022 17:35:30 -0700 (PDT) Received: by mail-pl1-x649.google.com with SMTP id y9-20020a17090322c900b00174c881abaeso4607506plg.6 for ; Tue, 30 Aug 2022 17:35:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc; bh=nNU9Bjqf9y2XiX7CZGxt5LtQZtYEQ0fRI0M+3kQYHd8=; b=nsUDSLmwiz2YIjGoJDWf0sAGexBLRtBGLNj+U0a0dxwdRSnDUJLZ/s81wWgXfPmfZC rcingM4u7HvJFWTBgWJYoy47ughU9OZmQ69i4DqRXTjNGW5TUGJAtBm24vA2koy20Z+W WFEt7S4TUlpmlrrMirREsdRXHPp3qTniXB67PD3UFg+egTtgi3vDgy/lBQtl6fgp7K4x na1upEaIRDzqldfvv3xrkoqoEluOHkX+4ctoSit8dSJRwikX9HoU6EP+/3rhGXZRoUT0 VfANzt47NFBIqN5xekmNQ7zAiDzyfupSXNkPPIW9bVZcUW6gXapvsysItmRXJxYhCoqs hACQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc; bh=nNU9Bjqf9y2XiX7CZGxt5LtQZtYEQ0fRI0M+3kQYHd8=; b=ah0COkVJRMzQ1g0SIeRrqnW89NP2oU0e0rKzuwE+DIGZxgC/nIFmUtRoxmiL8oKtSx VxaLaut5n7tzuiIOx6ZOf19iW4SZ+DaLVAiajPjRBfnW2Iy4XDEJLC4KIdXIz62Ek8R0 x6pu/RZxicopnQkLVNgz2BCAVy0uu4bIpp4m5WUBO7yNb0d/e+moJT0Gx+b9md4a14nS Rg/3vfEStoMblrqEVgpmMvQJ00zUBCVf83EruLZqFYi99RJjGutn7BdOvgImSd3yCX9s GnQ/EFQppUgR5aXbjBg06JDkPeXCBo1wLDY7No5Ar3ujaLHn+xDPDiDMTL6wWzaS8nhq QsCw== X-Gm-Message-State: ACgBeo1K5WbXdMd7ZrOv5xdsNEHEgrfqTNCWiIvI1EKX44EMheIOpEue 8nvnF7nbs/vvJQy1wkKosH6yG4gUDK0= X-Google-Smtp-Source: AA6agR6iq5WY+NgNU9ERXKVNHlEQ6M1HBHY81ehzHMF+0tkMrIik4W+FhStuptJ4GRhrcOxrXoHTiMQFa3I= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6a00:124d:b0:538:295a:1c47 with SMTP id u13-20020a056a00124d00b00538295a1c47mr13357367pfi.5.1661906114650; Tue, 30 Aug 2022 17:35:14 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 31 Aug 2022 00:34:50 +0000 In-Reply-To: <20220831003506.4117148-1-seanjc@google.com> Mime-Version: 1.0 References: <20220831003506.4117148-1-seanjc@google.com> X-Mailer: git-send-email 2.37.2.672.g94769d06f0-goog Message-ID: <20220831003506.4117148-4-seanjc@google.com> Subject: [PATCH 03/19] Revert "KVM: SVM: Introduce hybrid-AVIC mode" From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Suravee Suthikulpanit , Maxim Levitsky , Li RongQing Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Remove SVM's so called "hybrid-AVIC mode" and reinstate the restriction where AVIC is disabled if x2APIC is enabled. The argument that the "guest is not supposed to access xAPIC mmio when uses x2APIC" is flat out wrong. Activating x2APIC completely disables the xAPIC MMIO region, there is nothing that says the guest must not access that address. Concretely, KVM-Unit-Test's existing "apic" test fails the subtests that expect accesses to the APIC base region to not be emulated when x2APIC is enabled. Furthermore, allowing the guest to trigger MMIO emulation in a mode where KVM doesn't expect such emulation to occur is all kinds of dangerous. Tweak the restriction so that it only inhibits AVIC if x2APIC is actually enabled instead of inhibiting AVIC is x2APIC is exposed to the guest. This reverts commit 0e311d33bfbef86da130674e8528cc23e6acfe16. Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_host.h | 6 ++++++ arch/x86/kvm/svm/avic.c | 21 ++++++++++----------- 2 files changed, 16 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_hos= t.h index 2c96c43c313a..1f51411f3112 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1128,6 +1128,12 @@ enum kvm_apicv_inhibit { */ APICV_INHIBIT_REASON_PIT_REINJ, =20 + /* + * AVIC is inhibited because the vCPU has x2apic enabled and x2AVIC is + * not supported. + */ + APICV_INHIBIT_REASON_X2APIC, + /* * AVIC is disabled because SEV doesn't support it. */ diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c index f3a74c8284cb..1d516d658f9a 100644 --- a/arch/x86/kvm/svm/avic.c +++ b/arch/x86/kvm/svm/avic.c @@ -71,22 +71,12 @@ static void avic_activate_vmcb(struct vcpu_svm *svm) vmcb->control.avic_physical_id &=3D ~AVIC_PHYSICAL_MAX_INDEX_MASK; =20 vmcb->control.int_ctl |=3D AVIC_ENABLE_MASK; - - /* Note: - * KVM can support hybrid-AVIC mode, where KVM emulates x2APIC - * MSR accesses, while interrupt injection to a running vCPU - * can be achieved using AVIC doorbell. The AVIC hardware still - * accelerate MMIO accesses, but this does not cause any harm - * as the guest is not supposed to access xAPIC mmio when uses x2APIC. - */ - if (apic_x2apic_mode(svm->vcpu.arch.apic) && - avic_mode =3D=3D AVIC_MODE_X2) { + if (apic_x2apic_mode(svm->vcpu.arch.apic)) { vmcb->control.int_ctl |=3D X2APIC_MODE_MASK; vmcb->control.avic_physical_id |=3D X2AVIC_MAX_PHYSICAL_ID; /* Disabling MSR intercept for x2APIC registers */ svm_set_x2apic_msr_interception(svm, false); } else { - /* For xAVIC and hybrid-xAVIC modes */ vmcb->control.avic_physical_id |=3D AVIC_MAX_PHYSICAL_ID; /* Enabling MSR intercept for x2APIC registers */ svm_set_x2apic_msr_interception(svm, true); @@ -537,6 +527,14 @@ unsigned long avic_vcpu_get_apicv_inhibit_reasons(stru= ct kvm_vcpu *vcpu) { if (is_guest_mode(vcpu)) return APICV_INHIBIT_REASON_NESTED; + + /* + * AVIC must be disabled if x2AVIC isn't supported and the guest has + * x2APIC enabled. + */ + if (avic_mode !=3D AVIC_MODE_X2 && apic_x2apic_mode(vcpu->arch.apic)) + return APICV_INHIBIT_REASON_X2APIC; + return 0; } =20 @@ -993,6 +991,7 @@ bool avic_check_apicv_inhibit_reasons(enum kvm_apicv_in= hibit reason) BIT(APICV_INHIBIT_REASON_NESTED) | BIT(APICV_INHIBIT_REASON_IRQWIN) | BIT(APICV_INHIBIT_REASON_PIT_REINJ) | + BIT(APICV_INHIBIT_REASON_X2APIC) | BIT(APICV_INHIBIT_REASON_BLOCKIRQ) | BIT(APICV_INHIBIT_REASON_SEV) | BIT(APICV_INHIBIT_REASON_APIC_ID_MODIFIED) | --=20 2.37.2.672.g94769d06f0-goog