From patchwork Thu Jul 30 11:22:46 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Borntraeger X-Patchwork-Id: 6901621 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 5D2FEC05AC for ; Thu, 30 Jul 2015 11:22:38 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8010A20582 for ; Thu, 30 Jul 2015 11:22:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 718E6205B4 for ; Thu, 30 Jul 2015 11:22:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752860AbbG3LWd (ORCPT ); Thu, 30 Jul 2015 07:22:33 -0400 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:57648 "EHLO e06smtp12.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752634AbbG3LWa (ORCPT ); Thu, 30 Jul 2015 07:22:30 -0400 Received: from /spool/local by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Thu, 30 Jul 2015 12:22:25 +0100 X-Helo: d06dlp02.portsmouth.uk.ibm.com X-MailFrom: borntraeger@de.ibm.com X-RcptTo: linux-s390@vger.kernel.org Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id 8E4062190056; Thu, 30 Jul 2015 12:22:00 +0100 (BST) Received: from d06av04.portsmouth.uk.ibm.com (d06av04.portsmouth.uk.ibm.com [9.149.37.216]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t6UBMOOC35061780; Thu, 30 Jul 2015 11:22:24 GMT Received: from d06av04.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av04.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t6UBMMTo023152; Thu, 30 Jul 2015 05:22:24 -0600 Received: from tuxmaker.boeblingen.de.ibm.com (tuxmaker.boeblingen.de.ibm.com [9.152.85.9]) by d06av04.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVin) with ESMTP id t6UBMMXu023141 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 30 Jul 2015 05:22:22 -0600 Received: by tuxmaker.boeblingen.de.ibm.com (Postfix, from userid 25651) id 289191224458; Thu, 30 Jul 2015 13:22:22 +0200 (CEST) From: Christian Borntraeger To: Paolo Bonzini Cc: Alexander Graf , KVM , Cornelia Huck , Jens Freimann , linux-s390 , Christian Borntraeger Subject: [GIT PULL 1/1] KVM: s390: Fix hang VCPU hang/loop regression Date: Thu, 30 Jul 2015 13:22:46 +0200 Message-Id: <1438255366-25805-2-git-send-email-borntraeger@de.ibm.com> X-Mailer: git-send-email 2.3.0 In-Reply-To: <1438255366-25805-1-git-send-email-borntraeger@de.ibm.com> References: <1438255366-25805-1-git-send-email-borntraeger@de.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15073011-0009-0000-0000-0000050348CB Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-8.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP commit 785dbef407d8 ("KVM: s390: optimize round trip time in request handling") introduced a regression. This regression was seen with CPU hotplug in the guest and switching between 1 or 2 CPUs. This will set/reset the IBS control via synced request. Whenever we make a synced request, we first set the vcpu->requests bit and then block the vcpu. The handler, on the other hand, unblocks itself, processes vcpu->requests (by clearing them) and unblocks itself once again. Now, if the requester sleeps between setting of vcpu->requests and blocking, the handler will clear the vcpu->requests bit and try to unblock itself (although no bit is set). When the requester wakes up, it blocks the VCPU and we have a blocked VCPU without requests. Solution is to always unset the block bit. Signed-off-by: Christian Borntraeger Reviewed-by: David Hildenbrand Fixes: 785dbef407d8 ("KVM: s390: optimize round trip time in request handling") --- arch/s390/kvm/kvm-s390.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 2078f92..f32f843 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1742,10 +1742,10 @@ static bool ibs_enabled(struct kvm_vcpu *vcpu) static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu) { - if (!vcpu->requests) - return 0; retry: kvm_s390_vcpu_request_handled(vcpu); + if (!vcpu->requests) + return 0; /* * We use MMU_RELOAD just to re-arm the ipte notifier for the * guest prefix page. gmap_ipte_notify will wait on the ptl lock.