Re: [coreboot] [LinuxBIOS] Intel microcode revision code

[Carl-Daniel Hailfinger]

On 20.02.2008 19:29, Corey Osgood wrote:
> On Wed, Feb 20, 2008 at 1:09 PM, Carl-Daniel Hailfinger <
> [e-mail]> 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  [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
> > > > > 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?

OK, I was just used to the word from my Linux kernel and math background 
and thought everybody would understand it. "If and only if" is a longer 
phrase, but it seems to be understood by a wider audience, so I have 
dropped my objections against the change to that phrase.

Regards,
Carl-Daniel