linux-kernel - [patch, 2.6.22-rc6] fix nmi_watchdog=2 bootup hang, take #2

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Message-ID: <20070625185014.GA3935@elte.hu>
Date:	Mon, 25 Jun 2007 20:50:14 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Björn Steinbrink <B.Steinbrink@....de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: [patch, 2.6.22-rc6] fix nmi_watchdog=2 bootup hang, take #2


* Björn Steinbrink <B.Steinbrink@....de> wrote:

> > and of course i'm happy to test any patch that is simpler than the 
> > brutal revert i sent.
> 
> wrmsrl() looks broken, dropping the upper 32bits of the value to be 
> written. Does this help?

this did the trick, rc6 plus your fix and the NMI watchdog works again! 
Thanks! I suspect other code (oprofile?) broke due to this too.

below is a tidied up patch for upstream application. Must-have for 
2.6.22.

	Ingo

----------------->
From: Björn Steinbrink <B.Steinbrink@....de>
Subject: [patch, 2.6.22-rc6] fix nmi_watchdog=2 bootup hang, take #2

wrmsrl() is broken, dropping the upper 32bits of the value to be
written. This broke the NMI watchdog on AMD hardware. (and it
probably broke other code too.)

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 include/asm-i386/paravirt.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux/include/asm-i386/paravirt.h
===================================================================
--- linux.orig/include/asm-i386/paravirt.h
+++ linux/include/asm-i386/paravirt.h
@@ -539,7 +539,7 @@ static inline int paravirt_write_msr(uns
 	val = paravirt_read_msr(msr, &_err);	\
 } while(0)
 
-#define wrmsrl(msr,val)		((void)paravirt_write_msr(msr, val, 0))
+#define wrmsrl(msr,val)		wrmsr(msr, (u32)((u64)(val)), ((u64)(val))>>32)
 #define wrmsr_safe(msr,a,b)	paravirt_write_msr(msr, a, b)
 
 /* rdmsr with exception handling */
-
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