Messages in this thread Patch in this message | | | Date | Sun, 14 Jan 2007 10:29:26 +0100 | From | Ingo Molnar <> | Subject | [patch] disable NMI watchdog by default |
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From: Ingo Molnar <mingo@elte.hu> Subject: [patch] disable NMI watchdog by default
there's a new NMI watchdog related problem: KVM crashes on certain bzImages because ... we enable the NMI watchdog by default (even if the user does not ask for it) , and no other OS on this planet does that so KVM doesnt have emulation for that yet. So KVM injects a #GP, which crashes the Linux guest:
general protection fault: 0000 [#1] PREEMPT SMP Modules linked in: CPU: 0 EIP: 0060:[<c011a8ae>] Not tainted VLI EFLAGS: 00000246 (2.6.20-rc5-rt0 #3) EIP is at setup_apic_nmi_watchdog+0x26d/0x3d3
and no, i did /not/ request an nmi_watchdog on the boot command line!
Solution: turn off that darn thing! It's a debug tool, not a 'make life harder' tool!!
with this patch the KVM guest boots up just fine.
And with this my laptop (Lenovo T60) also stops its sporadic hard hanging (sometimes in acpi_init(), sometimes later during bootup, sometimes much later during actual use) as well. It hung with both nmi_watchdog=1 and nmi_watchdog=2, so it's generally the fact of NMI injection that is causing problems, not the NMI watchdog variant, nor any particular bootup code.
The patch is unintrusive.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Index: linux/include/asm-i386/nmi.h =================================================================== --- linux.orig/include/asm-i386/nmi.h +++ linux/include/asm-i386/nmi.h @@ -33,7 +33,7 @@ extern int nmi_watchdog_tick (struct pt_ extern atomic_t nmi_active; extern unsigned int nmi_watchdog; -#define NMI_DEFAULT -1 +#define NMI_DEFAULT 0 #define NMI_NONE 0 #define NMI_IO_APIC 1 #define NMI_LOCAL_APIC 2 Index: linux/include/asm-x86_64/nmi.h =================================================================== --- linux.orig/include/asm-x86_64/nmi.h +++ linux/include/asm-x86_64/nmi.h @@ -63,7 +63,7 @@ extern int setup_nmi_watchdog(char *); extern atomic_t nmi_active; extern unsigned int nmi_watchdog; -#define NMI_DEFAULT -1 +#define NMI_DEFAULT 0 #define NMI_NONE 0 #define NMI_IO_APIC 1 #define NMI_LOCAL_APIC 2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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