On 26.02.25 16:49, David Hildenbrand wrote:
On 24.02.25 22:14, Jane Chu wrote:When a process consumes a UE in a page, the memory failure handler attempts to collect information for a potential SIGBUS. If the page is an anonymous page, page_mapped_in_vma(page, vma) is invoked in order to 1. retrieve the vaddr from the process' address space, 2. verify that the vaddr is indeed mapped to the poisoned page, where 'page' is the precise small page with UE. It's been observed that when injecting poison to a non-head subpage of an anonymous hugetlb page, no SIGBUS show up; while injecting to the head page produces a SIGBUS. The casue is that, though hugetlb_walk() returns a valid pmd entry (on x86), but check_pte() detects mismatch between the head page per the pmd and the input subpage. Thus the vaddr is considered not mapped to the subpage and the process is not collected for SIGBUS purpose. This is the calling stack collect_procs_anon page_mapped_in_vma page_vma_mapped_walk hugetlb_walk huge_pte_lock check_pteWhy can't we require callers to never pass in subpages of hugetlb pages, and sanity check that this is the case?
To be precise: in collect_procs_anon() pass the head page of the hugetlb page, or in page_mapped_in_vma(), use the head page of the folio for hugetlb folios.
hugetlb folios are always entirely mapped, adding logic to detect if sub-pages are mapped doesn't make too much sense.
-- Cheers, David / dhildenb
