Another pmap related panic

[Mark Tinguely]

Thank-you,

The fact that pmap_pte_quick() panics on the untrue mutex should
indicate that it is possible that 2 processors may enter pmap_pte_quick()
at the same time and therefore it is possible to have the one processor
invalidate the VA/PA mapping using PADDR1/PMAP1. If that is true then
the first processor should trap/panic when dereferencing the VA address.

If the above is true, a PADDR1 mutex could be added, or use a seperate
PADDR/PMAP per processor. Looks like there is already mutex for the
copy maps. Did you want me to work up a test PADDR mutex?

--Mark.