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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E4F6C0015E for ; Wed, 26 Jul 2023 14:00:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233376AbjGZOAv (ORCPT ); Wed, 26 Jul 2023 10:00:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231346AbjGZOAr (ORCPT ); Wed, 26 Jul 2023 10:00:47 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20342211B for ; Wed, 26 Jul 2023 07:00:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1690379999; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=hI+xZjnjOx6iQYY+/HFIgbw6khCjngJ7Cxx7Odmq6DI=; b=C7yMC1i40LKp6E5PjnGS55hYeEKO25dAn2+zPF944DVSxQGjsJkckeVs26N0Ga1jk4a751 syyP90/AfriDqhZ1pvtDLk2zYRrpzGnwscq3SRNbd5iYGggGHvZuAqyb+YfFbHSFPtwlLx 6/ReQgeRRsmg61cc0ELEEjvU87UhrZ0= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-346-02aUmBj3PxCnqC9BrYH_Dw-1; Wed, 26 Jul 2023 09:59:56 -0400 X-MC-Unique: 02aUmBj3PxCnqC9BrYH_Dw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BF4EF8028B2; Wed, 26 Jul 2023 13:59:55 +0000 (UTC) Received: from localhost.localdomain (unknown [10.45.224.24]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2265840C2063; Wed, 26 Jul 2023 13:59:51 +0000 (UTC) From: Maxim Levitsky To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Borislav Petkov , Paolo Bonzini , Sean Christopherson , Dave Hansen , Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar , Maxim Levitsky Subject: [PATCH v2 0/3] Fix 'Spurious APIC interrupt (vector 0xFF) on CPU#n' issue Date: Wed, 26 Jul 2023 16:59:42 +0300 Message-Id: <20230726135945.260841-1-mlevitsk@redhat.com> Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Recently we found an issue which causes these error messages=0D to be sometimes logged if the guest has VFIO device attached:=0D =0D 'Spurious APIC interrupt (vector 0xFF) on CPU#0, should never happen'=0D =0D It was traced to the incorrect APICv inhibition bug which started with=0D 'KVM: x86: inhibit APICv/AVIC on changes to APIC ID or APIC base'=0D (All these issues are now fixed)=0D =0D However, there are valid cases for the APICv to be inhibited and it should = not=0D cause spurious interrupts to be injected to the guest.=0D =0D After some debug, the root cause was found and it is that __kvm_apic_update= _irr=0D doesn't set irr_pending which later triggers a int->unsigned char conversio= n=0D bug which leads to the wrong 0xFF injection.=0D =0D This also leads to an unbounded delay in injecting the interrupt and hurts= =0D performance.=0D =0D In addition to that, I also noticed that __kvm_apic_update_irr is not atomi= c=0D in regard to IRR, which can lead to an even harder to debug bug.=0D =0D V2: applied Paolo's feedback for the patch 1.=0D =0D Best regards,=0D Maxim Levitsky=0D =0D Maxim Levitsky (3):=0D KVM: x86: VMX: __kvm_apic_update_irr must update the IRR atomically=0D KVM: x86: VMX: set irr_pending in kvm_apic_update_irr=0D KVM: x86: check the kvm_cpu_get_interrupt result before using it=0D =0D arch/x86/kvm/lapic.c | 25 +++++++++++++++++--------=0D arch/x86/kvm/x86.c | 10 +++++++---=0D 2 files changed, 24 insertions(+), 11 deletions(-)=0D =0D -- =0D 2.26.3=0D =0D