From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992466Ab2K3Sw2 (ORCPT ); Fri, 30 Nov 2012 13:52:28 -0500 Received: from mail-ie0-f202.google.com ([209.85.223.202]:62091 "EHLO mail-ie0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161056Ab2K3SwX (ORCPT ); Fri, 30 Nov 2012 13:52:23 -0500 From: Vincent Palatin To: Ingo Molnar , "H. Peter Anvin" , linux-kernel@vger.kernel.org, Linus Torvalds Cc: Thomas Gleixner , x86@kernel.org, Peter Zijlstra , Jarkko Sakkinen , Duncan Laurie , Olof Johansson , Vincent Palatin Subject: [PATCH] x86, fpu: avoid FPU lazy restore after suspend Date: Fri, 30 Nov 2012 10:52:03 -0800 Message-Id: <1354301523-5252-2-git-send-email-vpalatin@chromium.org> X-Mailer: git-send-email 1.7.7.3 In-Reply-To: <1354301523-5252-1-git-send-email-vpalatin@chromium.org> References: <1354301523-5252-1-git-send-email-vpalatin@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When a cpu enters S3 state, the FPU state is lost. After resuming for S3, if we try to lazy restore the FPU for a process running on the same CPU, this will result in a corrupted FPU context. We can just invalidate the "fpu_owner_task", so nobody will try to lazy restore a state which no longer exists in the hardware. Tested with a 64-bit kernel on a 4-core Ivybridge CPU with eagerfpu=off, by doing thousands of suspend/resume cycles with 4 processes doing FPU operations running. Without the patch, a process is killed after a few hundreds cycles by a SIGFPE. The issue seems to exist since 3.4 (after the FPU lazy restore was actually implemented), to apply the change to 3.4, "this_cpu_write" needs to be replaced by percpu_write. Cc: Duncan Laurie Cc: Olof Johansson Cc: [v3.4+] # for 3.4 need to replace this_cpu_write by percpu_write Signed-off-by: Vincent Palatin --- arch/x86/kernel/smpboot.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index c80a33b..7610c58 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -68,6 +68,8 @@ #include #include #include +#include +#include #include #include #include @@ -1230,6 +1232,9 @@ int native_cpu_disable(void) clear_local_APIC(); cpu_disable_common(); + + /* the FPU context will be lost, nobody owns it */ + this_cpu_write(fpu_owner_task, NULL); return 0; } -- 1.7.7.3