[coreboot] [LinuxBIOS] Intel microcode revision code

Corey Osgood corey.osgood at gmail.com
Wed Feb 20 19:29:41 CET 2008


On Wed, Feb 20, 2008 at 1:09 PM, Carl-Daniel Hailfinger <
c-d.hailfinger.devel.2006 at gmx.net> wrote:

> On 20.02.2008 18:52, Stefan Reinauer wrote:
> > 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.
>
> Merriam-Webster agrees with me that "iff" is a word:
> http://www.merriam-webster.com/dictionary/iff
> So this is a valid sentence and I see no reason to change it. Unless the
> bit can be set even of no microcode update has been uploaded, "iff" is
> the only correct word.
>
> Regards,
> Carl-Daniel
>

Meriam-Webster and wikipedia might know, but not everyone does. Why can't we
just change it to "if and only if" instead of using an obscure word that
looks like a typo?

-Corey
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