From patchwork Fri Apr 1 03:52:47 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gibson X-Patchwork-Id: 8720141 Return-Path: X-Original-To: patchwork-qemu-devel@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 2BF09C0553 for ; Fri, 1 Apr 2016 03:52:01 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8322A20357 for ; Fri, 1 Apr 2016 03:52:00 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0F18F202F0 for ; Fri, 1 Apr 2016 03:51:56 +0000 (UTC) Received: from localhost ([::1]:35816 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alq7n-0008PO-8m for patchwork-qemu-devel@patchwork.kernel.org; Thu, 31 Mar 2016 23:51:55 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51356) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alq7b-0008Mo-KR for qemu-devel@nongnu.org; Thu, 31 Mar 2016 23:51:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1alq7X-0002X4-Ak for qemu-devel@nongnu.org; Thu, 31 Mar 2016 23:51:43 -0400 Received: from ozlabs.org ([103.22.144.67]:34359) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1alq7W-0002Wh-WA; Thu, 31 Mar 2016 23:51:39 -0400 Received: by ozlabs.org (Postfix, from userid 1007) id 3qbnVw2Rgvz9sC4; Fri, 1 Apr 2016 14:51:36 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gibson.dropbear.id.au; s=201602; t=1459482696; bh=WTfLXRdYKzO7XUwunV4j7m4esLtVvjuav4H2MNJdIJI=; h=From:To:Cc:Subject:Date:From; b=j9S3vx05OS10lWwO8K9J6fPxuf77M+gxgWNKPh0LlE1dRAxNH6bZ01Fb4cdwAw0sM fc8PtMdlLwzzwzN3M27hYChNC47l2DrPaIhibVb3Mh+MUwpGhJdANx/2YMDO6D/2qC dIkkqKNqYOw4N8X4mZiakyq1E9DOkhlvJiZXhlgw= From: David Gibson To: agraf@suse.de, pbonzini@redhat.com, aik@ozlabs.ru Date: Fri, 1 Apr 2016 14:52:47 +1100 Message-Id: <1459482767-12573-1-git-send-email-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.5.5 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 103.22.144.67 Cc: lvivier@redhat.com, peter.maydell@linaro.org, mdroth@linux.vnet.ibm.com, qemu-devel@nongnu.org, qemu-ppc@nongnu.org, David Gibson Subject: [Qemu-devel] [PATCH] target-ppc: Correct KVM synchronization for ppc_hash64_set_external_hpt() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI, T_DKIM_INVALID, UNPARSEABLE_RELAY autolearn=ham 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 ppc_hash64_set_external_hpt() was added in e5c0d3c "target-ppc: Add helpers for updating a CPU's SDR1 and external HPT". This helper contains a cpu_synchronize_state() since it may need to push state back to KVM afterwards. This turns out to break things when it is used in the reset path, which is the only current user. It appears that kvm_vcpu_dirty is not being set early in the reset path, so the cpu_synchronize_state() is clobbering state set up by the early part of the cpu reset path with stale state from KVM. To fix this, remove the cpu_synchronize_state() from ppc_hash64_set_external_hpt(). Any future non-reset-path users will need to manually invoke cpu_synchronize_state(). Reported-by: Laurent Vivier Signed-off-by: David Gibson --- target-ppc/mmu-hash64.c | 2 -- 1 file changed, 2 deletions(-) Paolo, Peter, This seems like the right minimal fix in the qemu-2.6 timeframe to fix the actual bug. However, longer term it seems like the correct thing to do might be to set kvm_vcpu_dirty early in the reset path. Thoughts? diff --git a/target-ppc/mmu-hash64.c b/target-ppc/mmu-hash64.c index 72c4ab5..caf41ce 100644 --- a/target-ppc/mmu-hash64.c +++ b/target-ppc/mmu-hash64.c @@ -283,8 +283,6 @@ void ppc_hash64_set_external_hpt(PowerPCCPU *cpu, void *hpt, int shift, CPUPPCState *env = &cpu->env; Error *local_err = NULL; - cpu_synchronize_state(CPU(cpu)); - if (hpt) { env->external_htab = hpt; } else {