Re: [patch] KVM: T60 resume fix

Ingo Molnar
2007-03-05T10:15:54Z

* Avi Kivity <avi@qumranet.com> wrote:

> > suspend/resume works fine now and there are no warning messages
> > whatsoever (with suspend simulation). Thanks Avi!
>
> Where do I find this suspend simulation? Sounds like a great suspend
> debugging tool.

it's just the simple hack below.

Ingo

------------------------>
Subject: [patch] suspend debugging: simulate suspend-to-RAM
From: Ingo Molnar <mingo@elte.hu>

most resume bugs are due to the kernel hanging or crashing while trying
to resume a specific device. It is extremely hard to debug such hangs
because often when the hang happens there's no console available yet.

Make debugging such bugs easier by offering a resume mode that does not
actually call into the BIOS to turn off the machine. This, in
combination with earlyprintk=serial,ttyS0,115200,keep ,
CONFIG_PM_DEBUG=y, CONFIG_DISABLE_CONSOLE_SUSPEND=y and
/sys/power/filter enables me to have a fully functional serial console
during the full suspend/resume cycle.

I debugged two suspend bugs in the -rt kernel this way already, so it's
pretty useful.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
Documentation/kernel-parameters.txt | 4 ++++
drivers/acpi/sleep/main.c | 15 ++++++++++++++-
include/linux/acpi.h | 1 +
kernel/sysctl.c | 8 ++++++++
4 files changed, 27 insertions(+), 1 deletion(-)

Index: linux/Documentation/kernel-parameters.txt
===================================================================
--- linux.orig/Documentation/kernel-parameters.txt
+++ linux/Documentation/kernel-parameters.txt
@@ -163,6 +163,10 @@ and is between 256 and 4096 characters.

acpi_osi= [HW,ACPI] empty param disables _OSI

+ acpi_simulate_suspend_to_ram
+ [KNL] Do not call into BIOS to do suspend-to-RAM
+ Format: <0/1>
+
acpi_serialize [HW,ACPI] force serialization of AML methods

acpi_skip_timer_override [HW,ACPI]
Index: linux/drivers/acpi/sleep/main.c
===================================================================
--- linux.orig/drivers/acpi/sleep/main.c
+++ linux/drivers/acpi/sleep/main.c
@@ -35,6 +35,14 @@ static u32 acpi_suspend_states[] = {

static int init_8259A_after_S1;

+/*
+ * simulate entry into the BIOS - this way the system will not
+ * be turned off for real, and the kernel's resume functionality
+ * can be debugged while still having some system capabilities
+ * left. This is especially useful in combination with /sys/power/filter.
+ */
+int acpi_simulate_suspend_to_ram;
+
/**
* acpi_pm_prepare - Do preliminary suspend work.
* @pm_state: suspend state we're entering.
@@ -91,7 +99,12 @@ static int acpi_pm_enter(suspend_state_t
break;

case PM_SUSPEND_MEM:
- do_suspend_lowlevel();
+ if (unlikely(acpi_simulate_suspend_to_ram)) {
+ printk(KERN_INFO "ACPI: simulating suspend-to-RAM: "
+ "not calling BIOS.\n");
+ } else {
+ do_suspend_lowlevel();
+ }
break;

case PM_SUSPEND_DISK:
Index: linux/include/linux/acpi.h
===================================================================
--- linux.orig/include/linux/acpi.h
+++ linux/include/linux/acpi.h
@@ -123,6 +123,7 @@ extern int pci_mmcfg_config_num;

extern int sbf_port;
extern unsigned long acpi_video_flags;
+extern int acpi_simulate_suspend_to_ram;

#else /* !CONFIG_ACPI */

Index: linux/kernel/sysctl.c
===================================================================
--- linux.orig/kernel/sysctl.c
+++ linux/kernel/sysctl.c
@@ -581,6 +581,14 @@ static ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_doulongvec_minmax,
},
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "acpi_simulate_suspend_to_ram",
+ .data = &acpi_simulate_suspend_to_ram,
+ .maxlen = sizeof (int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
#endif
#ifdef CONFIG_IA64
{