From patchwork Tue Jul 18 09:13:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maxim Levitsky X-Patchwork-Id: 13316905 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 4D0E0EB64DA for ; Tue, 18 Jul 2023 09:14:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230195AbjGRJOO (ORCPT ); Tue, 18 Jul 2023 05:14:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230259AbjGRJOL (ORCPT ); Tue, 18 Jul 2023 05:14:11 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A8F310F5 for ; Tue, 18 Jul 2023 02:13:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689671599; 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=lrWIzsgWi5PVFNBjLu8rbxMEA2rXGKqAaheIHU+uz9Y=; b=V+L52Io5BuZJYUVJDYZF5e92iYOTyIdRvWWu4R5LqOYQJqWVf6IfMunwKkYGwVv4s23GmC 7k0ZFFcia9wbHFbwC9jHQTj35ZZA79x5jDlm2W1wwPVlW2FYgtgIAVikC4e2quaG7P9zRL Bce+irksmoTdEw1UfS/ocRWKunHUHaA= 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-155-GdB-necKNRWkHIwBndRTSw-1; Tue, 18 Jul 2023 05:13:16 -0400 X-MC-Unique: GdB-necKNRWkHIwBndRTSw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 940B68D1685; Tue, 18 Jul 2023 09:13:15 +0000 (UTC) Received: from localhost.localdomain (unknown [10.45.224.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id 048FB1454142; Tue, 18 Jul 2023 09:13:11 +0000 (UTC) From: Maxim Levitsky To: kvm@vger.kernel.org Cc: "H. Peter Anvin" , Sean Christopherson , linux-kernel@vger.kernel.org, Thomas Gleixner , Paolo Bonzini , Ingo Molnar , Dave Hansen , x86@kernel.org, Borislav Petkov , Maxim Levitsky Subject: [PATCH 0/3] Fix 'Spurious APIC interrupt (vector 0xFF) on CPU#n' issue Date: Tue, 18 Jul 2023 12:13:07 +0300 Message-Id: <20230718091310.119672-1-mlevitsk@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 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. 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 | 23 +++++++++++++++-------- arch/x86/kvm/x86.c | 10 +++++++--- 2 files changed, 22 insertions(+), 11 deletions(-)