On Wed, Nov 30, 2011 at 12:59:36PM -0500, Konrad Rzeszutek Wilk wrote:
On Tue, Nov 29, 2011 at 07:34:28PM +0100, Borislav Petkov wrote:
On Tue, Nov 29, 2011 at 01:04:14PM -0500, Konrad Rzeszutek Wilk wrote:
This patch:
Borislav,
Thanks for your review comments. How does this patch look? I believe I touched upon all of the things you mentioned.
From eb6dbd80078312c428dde69e9313606b7513a2e6 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 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 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>
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.
The previous behavior before v3.0 was that pm_idle was set to default_idle irregardless 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 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..31f47ba 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(void) +{
- bool ret = !!pm_idle;
- pm_idle = default_idle;
- return ret;
+} 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..79dfb57 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();
}
From what I can see, you get the following callchain:
start_kernel |-> setup_arch |-> x86_init.oem.arch_setup = xen_arch_setup .... |-> check_bugs |-> identify_boot_cpu |-> identify_cpu |-> select_idle_routine
so xen_arch_setup will set pm_idle and select_idle_routine will honour it. I'm being told this is run either in the dom0 or the paravirt guest and if so, I don't see any issue with this for baremetal. So you can have my ACK provided this is tested on baremetal too.
Thanks.