Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753621AbbKQO7d (ORCPT ); Tue, 17 Nov 2015 09:59:33 -0500 Received: from smtp.citrix.com ([66.165.176.89]:21177 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753337AbbKQO7b (ORCPT ); Tue, 17 Nov 2015 09:59:31 -0500 X-IronPort-AV: E=Sophos;i="5.20,308,1444694400"; d="scan'208";a="312765076" Message-ID: <564B40CC.4030304@citrix.com> Date: Tue, 17 Nov 2015 14:59:24 +0000 From: Andrew Cooper User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 CC: Xen-devel , David Vrabel , Rusty Russell , "Thomas Gleixner" , Ingo Molnar , "H. Peter Anvin" , , , Konrad Rzeszutek Wilk , Boris Ostrovsky , , Subject: Re: [PATCH] x86/cpu: Fix SMAP check in PVOPS environments References: <1433323874-6927-1-git-send-email-andrew.cooper3@citrix.com> In-Reply-To: <1433323874-6927-1-git-send-email-andrew.cooper3@citrix.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 To: unlisted-recipients:; (no To-header on input) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2416 Lines: 62 Ping? None of the discussion on this thread altered the contents of this patch, and the bug is still present. ~Andrew On 03/06/15 10:31, Andrew Cooper wrote: > 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: Thomas Gleixner > CC: Ingo Molnar > CC: H. Peter Anvin > CC: x86@kernel.org > CC: linux-kernel@vger.kernel.org > CC: Konrad Rzeszutek Wilk > CC: Boris Ostrovsky > CC: xen-devel > CC: lguest@lists.ozlabs.org > CC: stable@vger.kernel.org > --- > 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 a62cf04..4f2fded 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -291,10 +291,9 @@ __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/