On Tue, Jul 15, 2025 at 04:06:29PM +0200, David Hildenbrand wrote: > I think at some point we discussed "when does the PMD-sized zeropage make > *any* sense on these weird arch configs" (512MiB on arm64 64bit) > > No idea who wants to waste half a gig on that at runtime either. Yeah this is a problem we _really_ need to solve. But obviously somewhat out of scope here. > > But yeah, we should let the arch code opt in whether it wants it or not (in > particular, maybe only on arm64 with CONFIG_PAGE_SIZE_4K) I don't think this should be an ARCH_HAS_xxx. Because that's saying 'this architecture has X', this isn't architecture scope. I suppose PMDs may vary in terms of how huge they are regardless of page table size actually. So maybe the best solution is a semantic one - just rename this to ARCH_WANT_STATIC_PMD_ZERO_PAGE And then put the page size selector in the arch code. For example in arm64 we have: select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36) So doing something similar here like: select ARCH_WANT_STATIC_PMD_ZERO_PAGE if ARM64_4K_PAGES Would do thie job and sort everything out. > > -- > Cheers, > > David / dhildenb > CHeers, Lorenzo
