Messages in this thread | | | Date | Fri, 19 May 2023 11:21:35 +0200 | From | David Hildenbrand <> | Subject | Re: [PATCH 1/3] mm: Move arch_do_swap_page() call to before swap_free() |
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>> Sorry, I meant actual anonymous memory pages, not shmem. Like, anonymous >> pages that are COW-shared due to fork() or KSM. >> >> How does MTE, in general, interact with that? Assume one process ends up >> modifying the tags ... and the page is COW-shared with a different >> process that should not observe these tag modifications. > > Tag modifications cause write faults if the page is read-only, so for > COW shared pages we would end up copying the page in the usual way, > which on arm64 would copy the tags as well via the copy_highpage hook > (see arch/arm64/mm/copypage.c).
Oh, that makes sense, thanks for pointing that out!
... and I can spot that KSM also checks the tag when de-duplicating: pages_identical() ends up calling memcmp_pages(), which knows how to deal with tags.
Interestingly, calc_checksum() does not seem to care about tags. But that simply implies that pages with the same content have same checksum, independent of the tag. And pages_identical() is the single source of truth.
-- Thanks,
David / dhildenb
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