On Mon, May 09, 2016 at 06:01:27PM +0100, Maciej W. Rozycki wrote: > On Mon, 9 May 2016, Ralf Baechle wrote: > > > Already PMC-Sierra's RM9000 / E9000 core had an extended ASID field, of > > 12 bits for 4096 ASID contexts. Afaics this was an extension derived > > in-house back in the wild days before everything had to be sanctioned by > > the architecture folks, so there is nothing in a config register to test > > for it. > > Couldn't you just probe it in EntryHi directly, by writing all-ones, > reading back and seeing how many bits have stuck? Note, the tlbinv feature in recent versions of MIPS32/MIPS64 arch has EHINV bit in bit 10 (if I remember right) of EntryHi, which marks whole tlb entry as invalid, and the small pages feature (for 1k pages) extends VPN field downwards to bit 11. Cheers James > > > PMCS simply extended the ASID field to 12 bits; no of the EntryHi bits > > which today would conflict doing so did exist back then. > > Especially as it was as simple like that -- bits 12:8 were hardwired to > zeros in the usual implementations back then. > > Maciej
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