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charset=UTF-8 Content-Transfer-Encoding: 8bit On 2/14/26 07:51, Mike Rapoport wrote: > Heh, it's x86's choice of memblock iterator that's rounding the ranges 😉 Ahh, good point. I was just assuming that the memblock iteration _had_ to be over PFNs. Silly me. > Maybe I miss some context, but my understanding is that for crash kernels > the unaccepted table is E820_TYPE_RESERVED and those are never added to > memblock.memory by e820 code, hence the call to memblock_add() in > reserve_unaccepted(). > > When x86 creates page tables, init_range_memory_mapping() walks > memblock.memory with for_each_mem_pfn_range() that rounds ranges that are > not page-aligned, which is normally fine, because it would mean that we > miss some partial pages that are divided between E820_RAM and > E820_SOMETHING_ELSE. > > And Kiryl's intention to round up unaccepted to page boundary seems correct > to me. It fixes the bug for sure. I'm more worried about the next feature, or the existing features that also only working because memory is page-aligned somewhere (even though it isn't guaranteed to remain that way). There are two choices for fixing this: One, we do Kiryl's fix plus checks to ensure that all the memblocks that generate direct mappings (is it _just_ the "memory" type?) are padded out to page-aligned boundaries. The other alternative is to do for_each_mem_range() and do the padding universally when creating the mappings. Maybe _also_ with warnings or maybe a pr_debug(). I do still think it's a little wonky for memblock_add()'s management of the "memory" type to allow unaligned arguments when that type is also used to create page-aligned mapping structures. Memblocks themselves obviously need to be byte-level, but I'm not sure it's the right thing for the "memory" type API.