On 7/17/25 07:52, David Hildenbrand wrote: > print_bad_pte() looks like something that should actually be a WARN > or similar, but historically it apparently has proven to be useful to > detect corruption of page tables even on production systems -- report > the issue and keep the system running to make it easier to actually detect > what is going wrong (e.g., multiple such messages might shed a light). > > As we want to unify vm_normal_page_*() handling for PTE/PMD/PUD, we'll have > to take care of print_bad_pte() as well. > > Let's prepare for using print_bad_pte() also for non-PTEs by adjusting the > implementation and renaming the function -- we'll rename it to what > we actually print: bad (page) mappings. Maybe it should be called > "print_bad_table_entry()"? We'll just call it "print_bad_page_map()" > because the assumption is that we are dealing with some (previously) > present page table entry that got corrupted in weird ways. > > Whether it is a PTE or something else will usually become obvious from the > page table dump or from the dumped stack. If ever required in the future, > we could pass the entry level type similar to "enum rmap_level". For now, > let's keep it simple. > > To make the function a bit more readable, factor out the ratelimit check > into is_bad_page_map_ratelimited() and place the dumping of page > table content into __dump_bad_page_map_pgtable(). We'll now dump > information from each level in a single line, and just stop the table > walk once we hit something that is not a present page table. > > Use print_bad_page_map() in vm_normal_page_pmd() similar to how we do it > for vm_normal_page(), now that we have a function that can handle it. > > The report will now look something like (dumping pgd to pmd values): > > [ 77.943408] BUG: Bad page map in process XXX entry:80000001233f5867 > [ 77.944077] addr:00007fd84bb1c000 vm_flags:08100071 anon_vma: ... > [ 77.945186] pgd:10a89f067 p4d:10a89f067 pud:10e5a2067 pmd:105327067 > > Not using pgdp_get(), because that does not work properly on some arm > configs where pgd_t is an array. Note that we are dumping all levels > even when levels are folded for simplicity. > > Signed-off-by: David Hildenbrand <da...@redhat.com>
Should this still use a WARN? If the admin sets panic-on-warn they have asked for "crash if anything goes wrong" and so that is what they should get. Otherwise the system will still stay up. -- Sincerely, Demi Marie Obenour (she/her/hers)
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