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_pte
Why can't we require callers to never pass in subpages of hugetlb pages,
and sanity check that this is the case?
--
Cheers,
David / dhildenb
