m68k: mm: Improve kernel_page_table()
With the PTE-tables now only being 256 bytes, allocating a full page
for them is a giant waste. Start by improving the boot time allocator
such that init_mm initialization will at least have optimal memory
density.
Much thanks to Will Deacon in help with debugging and ferreting out
lost information on these dusty MMUs.
Notes:
- _TABLE_MASK is reduced to account for the shorter (256 byte)
alignment of pte-tables, per the manual, table entries should only
ever have state in the low 4 bits (Used,WrProt,Desc1,Desc0) so it is
still longer than strictly required. (Thanks Will!!!)
- Also use kernel_page_table() for the 020/030 zero_pgtable case and
consequently remove the zero_pgtable init hack (will fix up later).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Greg Ungerer <gerg@linux-m68k.org>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Greg Ungerer <gerg@linux-m68k.org>
Link: https://lore.kernel.org/r/20200131125403.768263973@infradead.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
3 files changed