From patchwork Wed Jul 26 13:59:42 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxim Levitsky X-Patchwork-Id: 13328070 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 59BD9C001B0 for ; Wed, 26 Jul 2023 14:00:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233952AbjGZOAt (ORCPT ); Wed, 26 Jul 2023 10:00:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233393AbjGZOAr (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 20E881982 for ; Wed, 26 Jul 2023 07:00:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1690380000; 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=UujQctMtMaRBOjOSmqMvk6LYEtjlsPh7M1OD4I/UugyJaGWzAajX99xGMz/jED9Gok/URE 4vX1Sno2Jy5bN4300DaYsmE4DYYsbC6UmQqmFKlre+X4jwDMpfTlH9eBLPZBEXM2PTivVN I+gCb90aGcZomu9L/DRxK0UZOuJhtbs= 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> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Recently we found an issue which causes these error messages to be sometimes logged if the guest has VFIO device attached: 'Spurious APIC interrupt (vector 0xFF) on CPU#0, should never happen' It was traced to the incorrect APICv inhibition bug which started with 'KVM: x86: inhibit APICv/AVIC on changes to APIC ID or APIC base' (All these issues are now fixed) However, there are valid cases for the APICv to be inhibited and it should not cause spurious interrupts to be injected to the guest. After some debug, the root cause was found and it is that __kvm_apic_update_irr doesn't set irr_pending which later triggers a int->unsigned char conversion bug which leads to the wrong 0xFF injection. This also leads to an unbounded delay in injecting the interrupt and hurts performance. In addition to that, I also noticed that __kvm_apic_update_irr is not atomic in regard to IRR, which can lead to an even harder to debug bug. V2: applied Paolo's feedback for the patch 1. Best regards, Maxim Levitsky Maxim Levitsky (3): KVM: x86: VMX: __kvm_apic_update_irr must update the IRR atomically KVM: x86: VMX: set irr_pending in kvm_apic_update_irr KVM: x86: check the kvm_cpu_get_interrupt result before using it arch/x86/kvm/lapic.c | 25 +++++++++++++++++-------- arch/x86/kvm/x86.c | 10 +++++++--- 2 files changed, 24 insertions(+), 11 deletions(-)