Re: 3.2-rc2+: Reported regressions from 3.0 and 3.1

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Nov 22, 2011 at 08:54:12AM -0500, Konrad Rzeszutek Wilk wrote:
> > Subject    : Regression in 3.1 causes Xen to use wrong idle routine
> > Submitter  : Stefan Bader <stefan.bader@canonical.com>
> > Date       : 2011-10-26 10:24
> > Message-ID : 4EA7DFD1.9060608@canonical.com
> > References : http://marc.info/?l=linux-acpi&m=131962467924564&w=2
> 
> The patch mentioned in http://mid.gmane.org/20111115144004.GE22675@phenom.dumpdata.com 
> should do it. But the patch needs an Ack from ACPI/x86 folks.

This patch (mentioned in the URL above) fixes the issue. Could it be
applied to the x86 tree for 3.2 or get an Ack, please?

From 4f10ec7a7b9ff24657696aa98f25bcecde247373 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Mon, 21 Nov 2011 18:02:02 -0500
Subject: [PATCH] xen/pm_idle: Make pm_idle be default_idle under Xen.

This patch:

commit d91ee5863b71e8c90eaf6035bff3078a85e2e7b5
Author: Len Brown <len.brown@intel.com>
Date:   Fri Apr 1 18:28:35 2011 -0400

    cpuidle: replace xen access to x86 pm_idle and default_idle

    ..scribble on pm_idle and access default_idle,
   have it simply disable_cpuidle() so acpi_idle will not load and
   architecture default HLT will be used.

idea was to have one call - disable_cpuidle() which would make
pm_idle not be molested by other code. It disallows cpuidle_idle_call
and acpi_idle_call to not set pm_idle (which is excellent). But the
amd_e400_idle and mwait_idle can still setup pm_idle which we really
do not want. In case of mwait_idle we can hit some instances where:

Brought up 2 CPUs
invalid opcode: 0000 [#1] SMP
CPU 1
Modules linked in:

Pid: 0, comm: swapper Not tainted 3.1.0-0.rc6.git0.3.fc16.x86_64 #1
RIP: e030:[<ffffffff81015d1d>]  [<ffffffff81015d1d>] mwait_idle+0x6f/0xb4
RSP: e02b:ffff8801d28ddf10  EFLAGS: 00010082
RAX: ffff8801d28dc010 RBX: ffff8801d28ddfd8 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
RBP: ffff8801d28ddf10 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000001 R11: ffff8801d28ddfd8 R12: ffffffff81b590d0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801dff81000(0000) knlGS:0000000000000000
CS:  e033 DS: 002b ES: 002b CR0: 000000008005003b
CR2: 0000000000000000 CR3: 0000000001a05000 CR4: 0000000000002660
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000000
Process swapper (pid: 0, threadinfo ffff8801d28dc000, task ffff8801d28cae60)
Stack:
 ffff8801d28ddf40 ffffffff8100e2ed ffff8801dff8e390 c136dfe72feab515
 0000000000000000 0000000000000000 ffff8801d28ddf50 ffffffff8149ee78
 0000000000000000 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff8100e2ed>] cpu_idle+0xae/0xe8
 [<ffffffff8149ee78>] cpu_bringup_and_idle+0xe/0x10
RIP  [<ffffffff81015d1d>] mwait_idle+0x6f/0xb4
 RSP <ffff8801d28ddf10>

RH BZ #739499 and Ubuntu #881076

In 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.

Lets make pm_idle be default_idle to take care of that.

Reported-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 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 deletions(-)

diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index c2ff2a1..2d2f01c 100644
--- a/arch/x86/include/asm/system.h
+++ b/arch/x86/include/asm/system.h
@@ -401,6 +401,7 @@ extern unsigned long arch_align_stack(unsigned long sp);
 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);
 
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1f7f8c8..336b299 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -404,6 +404,14 @@ void default_idle(void)
 EXPORT_SYMBOL(default_idle);
 #endif
 
+bool set_pm_idle_to_default()
+{
+	if (!pm_idle) {
+		pm_idle = default_idle;
+		return true;
+	}
+	return false;
+}
 void stop_this_cpu(void *dummy)
 {
 	local_irq_disable();
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 46d6d21..7506181 100644
--- 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();
 }
-- 
1.7.7.3