From patchwork Thu Dec 17 00:39:08 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kamal Mostafa X-Patchwork-Id: 7867391 Return-Path: X-Original-To: patchwork-xen-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 2D55B9F350 for ; Thu, 17 Dec 2015 00:43:24 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 491EB203EB for ; Thu, 17 Dec 2015 00:43:23 +0000 (UTC) Received: from lists.xen.org (lists.xenproject.org [50.57.142.19]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 67952203E6 for ; Thu, 17 Dec 2015 00:43:22 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=lists.xen.org) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1a9Mck-0000RI-OO; Thu, 17 Dec 2015 00:40:50 +0000 Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1a9Mcj-0000Q3-TB for xen-devel@lists.xen.org; Thu, 17 Dec 2015 00:40:49 +0000 Received: from [193.109.254.147] by server-11.bemta-14.messagelabs.com id B7/32-28228-19402765; Thu, 17 Dec 2015 00:40:49 +0000 X-Env-Sender: kamal@canonical.com X-Msg-Ref: server-5.tower-27.messagelabs.com!1450312848!11532521!1 X-Originating-IP: [91.189.89.112] X-SpamReason: No, hits=0.0 required=7.0 tests= X-StarScan-Received: X-StarScan-Version: 7.35.1; banners=-,-,- X-VirusChecked: Checked Received: (qmail 22213 invoked from network); 17 Dec 2015 00:40:48 -0000 Received: from youngberry.canonical.com (HELO youngberry.canonical.com) (91.189.89.112) by server-5.tower-27.messagelabs.com with AES256-SHA encrypted SMTP; 17 Dec 2015 00:40:48 -0000 Received: from 1.general.kamal.us.vpn ([10.172.68.52] helo=fourier) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1a9Mce-0006q7-7n; Thu, 17 Dec 2015 00:40:44 +0000 Received: from kamal by fourier with local (Exim 4.82) (envelope-from ) id 1a9Mcb-0001Lp-W8; Wed, 16 Dec 2015 16:40:41 -0800 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Date: Wed, 16 Dec 2015 16:39:08 -0800 Message-Id: <1450312802-4938-25-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1450312802-4938-1-git-send-email-kamal@canonical.com> References: <1450312802-4938-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Cc: lguest@lists.ozlabs.org, Andrew Cooper , Kamal Mostafa , Rusty Russell , Xen-devel , Boris Ostrovsky , Thomas Gleixner Subject: [Xen-devel] [PATCH 3.13.y-ckt 24/78] x86/cpu: Fix SMAP check in PVOPS environments X-BeenThere: xen-devel@lists.xen.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, 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 3.13.11-ckt32 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Andrew Cooper commit 581b7f158fe0383b492acd1ce3fb4e99d4e57808 upstream. There appears to be no formal statement of what pv_irq_ops.save_fl() is supposed to return precisely. Native returns the full flags, while lguest and Xen only return the Interrupt Flag, and both have comments by the implementations stating that only the Interrupt Flag is looked at. This may have been true when initially implemented, but no longer is. To make matters worse, the Xen PVOP leaves the upper bits undefined, making the BUG_ON() undefined behaviour. Experimentally, this now trips for 32bit PV guests on Broadwell hardware. The BUG_ON() is consistent for an individual build, but not consistent for all builds. It has also been a sitting timebomb since SMAP support was introduced. Use native_save_fl() instead, which will obtain an accurate view of the AC flag. Signed-off-by: Andrew Cooper Reviewed-by: David Vrabel Tested-by: Rusty Russell Cc: Rusty Russell Cc: Konrad Rzeszutek Wilk Cc: Boris Ostrovsky Cc: Cc: Xen-devel Link: http://lkml.kernel.org/r/1433323874-6927-1-git-send-email-andrew.cooper3@citrix.com Signed-off-by: Thomas Gleixner Signed-off-by: Kamal Mostafa --- arch/x86/kernel/cpu/common.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 37c4f31..a1f7c91 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -280,10 +280,9 @@ __setup("nosmap", setup_disable_smap); static __always_inline void setup_smap(struct cpuinfo_x86 *c) { - unsigned long eflags; + unsigned long eflags = native_save_fl(); /* This should have been cleared long ago */ - raw_local_save_flags(eflags); BUG_ON(eflags & X86_EFLAGS_AC); if (cpu_has(c, X86_FEATURE_SMAP)) {