On Monday 05 March 2007 07:20, Ingo Molnar wrote: > > Linus, > > Andrew sent the patch below (which is now months old and has been in -mm > for some time) towards Andi's tree 4 weeks ago, but apparently it fell > into a black hole there - the patch is still not upstream! > > This is a must-have for v2.6.21
I agree. There are multiple machines not booting because of nmi_watchdog. Some of them are documented here: http://bugzilla.kernel.org/show_bug.cgi?id=7839 We used to think this was the "nolapic" bug, but it is actually the "nmi_watchdog=0" bug. -Len > Frankly, i find it ridiculous that i had to write more than 10 emails > about this stupid topic already, while i'm the original author of this > feature to begin with. The "do not enable by default debug features that > break certain systems" concept is obvious to me. > > This category of regressions has been introduced by Andi when he made > the NMI watchdog the default in certain scenarios at around v2.6.18 - > over my repeated objections. Andi Cc:-ed :-) > > Ingo > > ----- Forwarded message from Ingo Molnar <[EMAIL PROTECTED]> ----- > > From: Ingo Molnar <[EMAIL PROTECTED]> > 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 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. > > The patch is unintrusive. > > Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]> > > 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 [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
