Messages in this thread | | | Date | Tue, 28 Nov 2023 17:58:55 +0100 | Subject | Re: [PATCH RFC v2 06/27] mm: page_alloc: Allow an arch to hook early into free_pages_prepare() | From | David Hildenbrand <> |
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On 27.11.23 14:03, Alexandru Elisei wrote: > Hi, > > On Fri, Nov 24, 2023 at 08:36:52PM +0100, David Hildenbrand wrote: >> On 19.11.23 17:57, Alexandru Elisei wrote: >>> Add arch_free_pages_prepare() hook that is called before that page flags >>> are cleared. This will be used by arm64 when explicit management of tag >>> storage pages is enabled. >> >> Can you elaborate a bit what exactly will be done by that code with that >> information? > > Of course. > > The MTE code that is in the kernel today uses the PG_arch_2 page flag, which it > renames to PG_mte_tagged, to track if a page has been mapped with tagging > enabled. That flag is cleared by free_pages_prepare() when it does: > > page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; > > When tag storage management is enabled, tag storage is reserved for a page if > and only if the page is mapped as tagged. When a page is freed, the code looks > at the PG_mte_tagged flag to determine if the page was mapped as tagged, and > therefore has tag storage reserved, to determine if the corresponding tag > storage should also be freed. > > I have considered using arch_free_page(), but free_pages_prepare() calls the > function after the flags are cleared. > > Does that answer your question?
Yes, please add some of that to the patch description!
-- Cheers,
David / dhildenb
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