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Date:	Sun, 25 Mar 2012 12:27:23 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jan Beulich <JBeulich@...e.com>
Subject: Re: [GIT PULL] x86, microcode fixes for 3.2

On 12/05/2011 07:10 AM, Borislav Petkov wrote:
> 
> diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
> index 084ef95..95203d4 100644
> --- a/arch/x86/include/asm/msr.h
> +++ b/arch/x86/include/asm/msr.h
> @@ -169,7 +169,14 @@ static inline int wrmsr_safe(unsigned msr, unsigned low, unsigned high)
>  	return native_write_msr_safe(msr, low, high);
>  }
>  
> -/* rdmsr with exception handling */
> +/*
> + * rdmsr with exception handling.
> + *
> + * Please note that the exception handling works only after we've
> + * switched to the "smart" #GP handler in trap_init() which knows about
> + * exception tables - using this macro earlier than that causes machine
> + * hangs on boxes which do not implement the @msr in the first argument.
> + */
>  #define rdmsr_safe(msr, p1, p2)					\
>  ({								\
>  	int __err;						\

I keep wondering if we couldn't have the early-static trap handlers be
aware of exception tables, too; they wouldn't have to worry about
modules and so it would be reasonably easy.

	-hpa
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