[coreboot] [LinuxBIOS] Intel microcode revision code

[Stefan Reinauer]

Carl-Daniel Hailfinger wrote:
> On 20.02.2008 17:19, Stefan Reinauer wrote:
>   
>> * ron minnich <rminnich at gmail.com> [071212 17:19]:
>>   
>>     
>>>> Question to you guys: why is the first wrmsr instruction there? From my
>>>> understanding, by not properly initialising ECX, EAX and EDX this will
>>>> overwrite whatever is in the MSR pointed to by ECX?!
>>>>
>>>> BTW I tried out your code on our target hardware (Intel Celeron M, 600 MHz)
>>>> and with that first wrmsr line in place it hangs and without it, it runs
>>>> just fine.
>>>>       
>>>>         
>>> Thanks Martin. That looks like quite a nice bug catch you've done :-)
>>>     
>>>       
>> Here's a patch that resolves the issue.
>>
>> Signed-off-by: Stefan Reinauer <stepan at coresystems.de>
>>
>> Index: src/cpu/intel/microcode/microcode.c
>> ===================================================================
>> --- src/cpu/intel/microcode/microcode.c	(revision 3111)
>> +++ src/cpu/intel/microcode/microcode.c	(working copy)
>> @@ -33,7 +33,6 @@
>>  	 */
>>  	msr_t msr;
>>  	__asm__ volatile (
>> -		"wrmsr\n\t"
>>   
>>     
>
> ACK.
>
>   
>>  		"xorl %%eax, %%eax\n\t"
>>  		"xorl %%edx, %%edx\n\t"
>>  		"movl $0x8b, %%ecx\n\t"
>> @@ -60,7 +59,7 @@
>>  	char *c;
>>  	msr_t msr;
>>  	
>> -	/* cpuid sets msr 0x8B iff a microcode update has been loaded. */
>> +	/* cpuid sets msr 0x8B if a microcode update has been loaded. */
>>   
>>     
>
> NACK. "IFF" is shorthand for "if and only if", see 
> http://en.wikipedia.org/wiki/If_and_only_if
>   

That's silly. This is not a mathematical expression nor a philosophical 
disquisition but a sentence. I am not even convinced that it was meant 
that way rather than being just a typo. If you have reasons to assume it 
means "If and only if" then let's write it that way.

Stefan


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