Hi, On Tue, Nov 28, 2023 at 05:58:55PM +0100, David Hildenbrand wrote: > 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! Will do! Thanks, Alex > > -- > Cheers, > > David / dhildenb >
