From 6ebf622b2577c50b1f496bd6a5e8739e55ae7b1c Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@elte.hu> Date: Mon, 5 Mar 2007 13:20:11 +0100 Subject: [PATCH] [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 stopped 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. [ NMI breaks on some systems, esp in combination with SMM -Arjan ] Signed-off-by: Ingo Molnar <mingo@elte.hu> Acked-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- include/asm-i386/nmi.h | 2 +- include/asm-x86_64/nmi.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/asm-i386/nmi.h b/include/asm-i386/nmi.h index b04333ea6f31e..64544cb85d6a4 100644 --- a/include/asm-i386/nmi.h +++ b/include/asm-i386/nmi.h @@ -33,7 +33,7 @@ extern int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason); 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 diff --git a/include/asm-x86_64/nmi.h b/include/asm-x86_64/nmi.h index 72375e7d32a89..ceb3d8dac33d4 100644 --- a/include/asm-x86_64/nmi.h +++ b/include/asm-x86_64/nmi.h @@ -64,7 +64,7 @@ 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 -- 2.30.2