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    SubjectRe: MTRR control
    Richard Gooch wrote:
    > Alan Cox writes:
    > > > Another problem with proform-1.0 is that it states that it doesn't
    > > > work with SMP. Why is this so? Is it simply because the MTRRs of the
    > > > CPU which happened to run insmod are modified, but not those of the
    > >
    > > Yep
    > >
    > > > other CPU(s)? In that case all that is needed is some mechanism to run
    > > > this bit of code for all CPUs.
    > >
    > > Thats all there is too it. The x86 SMP code has some message passing it
    > > uses for sending certain inter CPU events, adding a "sync mtrr" message
    > > should do the trick.
    > OK, I'll have a look at that. Another question: I've been looking at
    > the sysctl interface, and I'm not so sure that it is really what I
    > want to use. It seems to be more tuned to fiddling kernel parameters
    > rather than hardware registers. So I'm thinking of simply adding a R/W
    > entry like /proc/mtrr which would yield something like:
    > reg00: base=0x00000000 ( 0MB), range= 128MB: write-back
    > reg01: base=0xf8000000 (3968MB), range= 4MB: write-combining
    > when reading and would require you to write the following to create an
    > entry:
    > 0xf8000000 0x400000 write-combining
    > and the following to remove an entry:
    > 0xf8000000 0x400000 remove
    > and /proc/mtrr would only exist on a PPro. Does this scheme sound
    > reasonable (read: clean enough)?

    This could probably be extended to the Cyrix 6x86[MX] processor's ARR
    registers which seem to do a similar function.


    Brian Gerst

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