K6-III/450 MTRR support

K6-III/450 MTRR support

[Bob Tracy]

Anyone got a quick way to determine whether MTRR support is working
correctly on this old CPU?  "cat /proc/mtrr" doesn't show anything
configured in cases where I used to see a few entries.  Using the "nv"
driver (Xorg 1.6.3 dated 2009-07-31: latest version for Slackware 13)
produces two error messages...  This one appears in syslog:

kernel: mtrr: no MTRR for d0000000,4000000 found

and this one appears as the last line of output to the virtual console
after shutting down the X server:

waiting for X server to shut down error setting MTRR (base = 0xd0000000, \
size = 0x04000000, type = 1) Invalid argument (22)

Here are the applicable kernel config lines: if the config doesn't make
sense, I'm sure someone will let me know.  The last time I *know* MTRRs
worked properly was before the PAT and SANITIZER options showed up:
yeah, that far back...

CONFIG_MTRR=y
CONFIG_MTRR_SANITIZER=y
CONFIG_MTRR_SANITIZER_ENABLE_DEFAULT=1
CONFIG_MTRR_SANITIZER_SPARE_REG_NR_DEFAULT=1
CONFIG_X86_PAT=y

--Bob