panic: incorrect npmc count

[This may be a duplicate because I forgot to update my subscription
 after changing address but I've also corrected a typo]

(I've copied fabient_at_ because r233628 appears to have been the last
commit in this area).

I've just updated a P4 test box from r232545 to r235127 and it now
panics during boot:
 panic: [intel,202] incorrect npmc count 35
Looking at sys/dev/hwpmc/hmpmc_intel.c line 202, the expected
npmc count is 19.

When I look at the actual code in pmc_intel_initialize():
pmc_mdep_alloc() initialises pmd_npmc to zero and then increments
  it by SOFT_NPMCS (16) in pmc_soft_initialize().
pmc_tsc_initialize() then increments it by TSC_NPMCS (1)
pmc_p4_initialize() then increments it by P4_NPMCS (18)
This totals 35 (as per the panic message).

Can someone explain the KASSERT() that expects 19 - it boils down to
KASSERT(0+16+1+18 == 1+18, ...)
I gather not many people are running -current on a P4.

-- 
Peter Jeremy