From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932891Ab1LPTwF (ORCPT ); Fri, 16 Dec 2011 14:52:05 -0500 Received: from cantor2.suse.de ([195.135.220.15]:45113 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932836Ab1LPTuy (ORCPT ); Fri, 16 Dec 2011 14:50:54 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Fri Dec 16 11:45:59 2011 Message-Id: <20111216194559.388964698@clark.kroah.org> User-Agent: quilt/0.50-24.1 Date: Fri, 16 Dec 2011 11:45:30 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Konrad Rzeszutek Wilk Subject: [33/53] xen/pm_idle: Make pm_idle be default_idle under Xen. In-Reply-To: <20111216194613.GA18395@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Konrad Rzeszutek Wilk commit e5fd47bfab2df0c2184cc0bf4245d8e1bb7724fb upstream. The idea behind commit d91ee5863b71 ("cpuidle: replace xen access to x86 pm_idle and default_idle") was to have one call - disable_cpuidle() which would make pm_idle not be molested by other code. It disallows cpuidle_idle_call to be set to pm_idle (which is excellent). But in the select_idle_routine() and idle_setup(), the pm_idle can still be set to either: amd_e400_idle, mwait_idle or default_idle. This depends on some CPU flags (MWAIT) and in AMD case on the type of CPU. In case of mwait_idle we can hit some instances where the hypervisor (Amazon EC2 specifically) sets the MWAIT and we get: Brought up 2 CPUs invalid opcode: 0000 [#1] SMP Pid: 0, comm: swapper Not tainted 3.1.0-0.rc6.git0.3.fc16.x86_64 #1 RIP: e030:[] [] mwait_idle+0x6f/0xb4 ... Call Trace: [] cpu_idle+0xae/0xe8 [] cpu_bringup_and_idle+0xe/0x10 RIP [] mwait_idle+0x6f/0xb4 RSP In the case of amd_e400_idle we don't get so spectacular crashes, but we do end up making an MSR which is trapped in the hypervisor, and then follow it up with a yield hypercall. Meaning we end up going to hypervisor twice instead of just once. The previous behavior before v3.0 was that pm_idle was set to default_idle regardless of select_idle_routine/idle_setup. We want to do that, but only for one specific case: Xen. This patch does that. Fixes RH BZ #739499 and Ubuntu #881076 Reported-by: Stefan Bader Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/system.h | 1 + arch/x86/kernel/process.c | 8 ++++++++ arch/x86/xen/setup.c | 2 +- 3 files changed, 10 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -401,6 +401,7 @@ extern unsigned long arch_align_stack(un extern void free_init_pages(char *what, unsigned long begin, unsigned long end); void default_idle(void); +bool set_pm_idle_to_default(void); void stop_this_cpu(void *dummy); --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -403,6 +403,14 @@ void default_idle(void) EXPORT_SYMBOL(default_idle); #endif +bool set_pm_idle_to_default(void) +{ + bool ret = !!pm_idle; + + pm_idle = default_idle; + + return ret; +} void stop_this_cpu(void *dummy) { local_irq_disable(); --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -448,6 +448,6 @@ void __init xen_arch_setup(void) #endif disable_cpuidle(); boot_option_idle_override = IDLE_HALT; - + WARN_ON(set_pm_idle_to_default()); fiddle_vdso(); }