Re: [PATCH] mm/huge_memory: Initialise the tags of the huge zero folio

[David Hildenbrand <david@redhat.com>]

On 31.10.25 17:57, Catalin Marinas wrote:
> On arm64 with MTE enabled, a page mapped as Normal Tagged (PROT_MTE) in
> user space will need to have its allocation tags initialised. This is
> normally done in the arm64 set_pte_at() after checking the memory
> attributes. Such page is also marked with the PG_mte_tagged flag to
> avoid subsequent clearing. Since this relies on having a struct page,
> pte_special() mappings are ignored.
> 
> Commit d82d09e48219 ("mm/huge_memory: mark PMD mappings of the huge zero
> folio special") maps the huge zero folio special and the arm64
> set_pmd_at() will no longer zero the tags. There is no guarantee that
> the tags are zero, especially if parts of this huge page have been
> previously tagged.
> 
> Allocate the huge zero folio with the __GFP_ZEROTAGS flag. In addition,
> do not warn in the arm64 __access_remote_tags() when reading tags from
> the huge zero page.
> 
> Fixes: d82d09e48219 ("mm/huge_memory: mark PMD mappings of the huge zero folio special")
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Will Deacon <will@kernel.org>

Acked-by: David Hildenbrand <david@redhat.com>

Thanks, Catalin!

-- 
Cheers

David / dhildenb