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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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