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Christophe Leroy wrote: > I can help with powerpc 8xx. It is a 32 bits powerpc. The PGD has 1024 > entries, that means each entry maps 4M. > > Page sizes are 4k, 16k, 512k and 8M. > > For the 8M pages we use hugepd with a single entry. The two related PGD > entries point to the same hugepd. > > For the other sizes, they are in standard page tables. 16k pages appear > 4 times in the page table. 512k entries appear 128 times in the page > table. > > When the PGD entry has _PMD_PAGE_8M bits, the PMD entry points to a > hugepd with holds the single 8M entry. > > In the PTE, we have two bits: _PAGE_SPS and _PAGE_HUGE > > _PAGE_HUGE means it is a 512k page > _PAGE_SPS means it is not a 4k page > > The kernel can by build either with 4k pages as standard page size, or > 16k pages. It doesn't change the page table layout though. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20201126121121.364451610@infradead.org