* Ingo Molnar <[email protected]> wrote:
> Subject: [patch] call reboot notifier list when doing an emergency reboot
> From: Ingo Molnar <[email protected]>
>
> my laptop (Lenovo T60) hangs during reboot if the shutdown notifiers are
> not called. So the following command, which on other systems i use as a
> quick way to reboot into a new kernel:
>
> echo b > /proc/sysrq-trigger
>
> just hangs indefinitely after the kernel prints "Restarting system".
i also figured out which one of the many reboot notifiers makes the
crutial difference: it's kvm_reboot().
So i think we should do the patch below - this makes reboot work even in
atomic contexts. (My previous patch makes sense nevertheless, as reboot
notifiers are quite useful in general, even during SysRq-b or panic
reboots. For example the SATA disk caches are flushed.)
I have tested this without the other kernel/sys.c patch, and this solves
the hung reboot problem equally well.
Ingo
--------------------->
Subject: [patch] KVM: do VMXOFF upon reboot
From: Ingo Molnar <[email protected]>
my laptop's BIOS apparently gets confused if the kernel tries to
reboot without first turning VT context off, which results in a
hung (emergency-)reboot. So make sure this happens, right before
we reboot.
( NOTE: this is a dual-core system, but only the core where the
BIOS executes seems to be affected - the other core can have an
active VT context just fine - so we dont have to risk reboot
robustness by doing a CPU cross-call in the emergency reboot
handler. )
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/i386/kernel/reboot.c | 8 ++++++++
arch/x86_64/kernel/reboot.c | 7 +++++++
2 files changed, 15 insertions(+)
Index: linux/arch/i386/kernel/reboot.c
===================================================================
--- linux.orig/arch/i386/kernel/reboot.c
+++ linux/arch/i386/kernel/reboot.c
@@ -318,6 +318,14 @@ void machine_shutdown(void)
void machine_emergency_restart(void)
{
+ unsigned long ecx = cpuid_ecx(1);
+
+ /*
+ * Disable any possibly active VT context (if VT supported):
+ */
+ if (test_bit(5, &ecx)) /* has VT support */
+ asm volatile (".byte 0x0f, 0x01, 0xc4"); /* vmxoff */
+
if (!reboot_thru_bios) {
if (efi_enabled) {
efi.reset_system(EFI_RESET_COLD, EFI_SUCCESS, 0, NULL);
Index: linux/arch/x86_64/kernel/reboot.c
===================================================================
--- linux.orig/arch/x86_64/kernel/reboot.c
+++ linux/arch/x86_64/kernel/reboot.c
@@ -114,8 +114,15 @@ void machine_shutdown(void)
void machine_emergency_restart(void)
{
+ unsigned long ecx = cpuid_ecx(1);
int i;
+ /*
+ * Disable any possibly active VT context (if VT supported):
+ */
+ if (test_bit(5, &ecx)) /* has VT support */
+ asm volatile (".byte 0x0f, 0x01, 0xc4"); /* vmxoff */
+
/* Tell the BIOS if we want cold or warm reboot */
*((unsigned short *)__va(0x472)) = reboot_mode;
-
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