Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758317AbbKSKNW (ORCPT ); Thu, 19 Nov 2015 05:13:22 -0500 Received: from terminus.zytor.com ([198.137.202.10]:39638 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757973AbbKSKNT (ORCPT ); Thu, 19 Nov 2015 05:13:19 -0500 Date: Thu, 19 Nov 2015 02:12:51 -0800 From: tip-bot for Andrew Cooper Message-ID: Cc: rusty@rustcorp.com.au, linux-kernel@vger.kernel.org, mingo@kernel.org, david.vrabel@citrix.com, tglx@linutronix.de, xen-devel@lists.xen.org, boris.ostrovsky@oracle.com, hpa@zytor.com, lguest@lists.ozlabs.org, konrad.wilk@oracle.com, andrew.cooper3@citrix.com Reply-To: rusty@rustcorp.com.au, linux-kernel@vger.kernel.org, tglx@linutronix.de, david.vrabel@citrix.com, mingo@kernel.org, xen-devel@lists.xen.org, boris.ostrovsky@oracle.com, lguest@lists.ozlabs.org, hpa@zytor.com, andrew.cooper3@citrix.com, konrad.wilk@oracle.com In-Reply-To: <1433323874-6927-1-git-send-email-andrew.cooper3@citrix.com> References: <1433323874-6927-1-git-send-email-andrew.cooper3@citrix.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/cpu: Fix SMAP check in PVOPS environments Git-Commit-ID: 581b7f158fe0383b492acd1ce3fb4e99d4e57808 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2552 Lines: 60 Commit-ID: 581b7f158fe0383b492acd1ce3fb4e99d4e57808 Gitweb: http://git.kernel.org/tip/581b7f158fe0383b492acd1ce3fb4e99d4e57808 Author: Andrew Cooper AuthorDate: Wed, 3 Jun 2015 10:31:14 +0100 Committer: Thomas Gleixner CommitDate: Thu, 19 Nov 2015 11:07:49 +0100 x86/cpu: Fix SMAP check in PVOPS environments 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 CC: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1433323874-6927-1-git-send-email-andrew.cooper3@citrix.com Signed-off-by: Thomas Gleixner --- 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 4ddd780..c2b7522 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -273,10 +273,9 @@ __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)) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/