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SubjectRe: [patch-2.3.46-p2] P6 microcode update support
Linus Torvalds wrote:
>
> On Wed, 16 Feb 2000, Tigran Aivazian wrote:
> >
> > I tested both SMP and UP kernels on my home SMP machine (CPU
> > signature=0x673, upgraded to revision=14 microcode)
>
> The code looks ok, but "mtrr.c"?
>
> That just doesn't make any sense. Why not a separate simple driver?
>
> Linus

Oh ok. I wanted to do that but I thought you would say "why having a
separate simple driver if you can just put it in.. say mtrr.c?" :)
Besides, it is from mtrr.c I learned that Linux can do function call
IPIs like on other x86 UNIX flavours. Actually I wanted an ioctl on
/proc/cpuinfo but that meant upgrading it from the status of simple
"misc" proc file and mtrr already had ioctls.

Ok, I will make a separate simple character driver with a single ioctl
(to not have to deal with issues of multiple read(2)), although being
able to just say "cat microcode > /dev/microcode" would be nice.
Also, more importantly, Intel manual says "the update must run in the
early stages of POST and always before L2 cache controllers are
initialized". I ignored it and it still worked fine. However, on the bus
to work this morning I thought "perhaps I should use some MSRs to
disable cache and re-enable it?". I will think on this in the background
but first rewrite it as a char driver.

Thanks for your feedback,

I suppose I need to ask Peter to grant me minor=180 of the major=10
(misc character drivers)? And most difficult part - think of a short
name prefix abbreviation for "Intel P6 Microcode Update Device" - IMU?
/dev/imu

Regards,
Tigran.

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