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SubjectRe: Where to call L2 cache enabling code from?
On Fri, Apr 14, 2006 at 12:49:49PM -0400, Steve Snyder wrote:
> On Friday 14 April 2006 11:46 am, Alan Cox wrote:
> > On Gwe, 2006-04-14 at 11:05 -0400, Steve Snyder wrote:
> > > I have a machine in which the BIOS does not enable the Pentium3's L2
> > > cache at boot time. At what point in the kernel init process
> > > can/should I call the code to enable the cache?
> >
> > What part of the cache setup is not done correctly ? The mtrr registers
> > or other things ?
> It's not that the kernel is failing in any respect. The BIOS simply does
> not enable the on-CPU L2 cache at power-on. (The machine originally
> shipped with a Pentium2, and doesn't know how to enable the L2 cache on
> the Pentium3 that is now running in it.)
> I've got a small device driver that enables the L2 cache. It works fine
> when build as a module and loaded after booting has completed. My goal
> is to move the code into the kernel so that it is run early in the kernel
> init process. I expect that having the L2 cache go from "0KB" to 256KB
> will improve boot time greatly, as well as informing the kernel from the
> get-go of the true capabilities of this processor.
> Getting the code into the kernel image is a no-brainer. But once it is
> built into the kernel, at what point should I call it?

arch/i386/kernel/cpu/intel.c has a bunch of workarounds for various
issues. Is there a valid use-case for ever booting with cache disabled
though? If so, this should probably be a boot-time option to enable it.


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