madvise_cold_or_pageout_pte_range() takes pmd_trans_huge_lock(), whose pmd_is_huge() check returns true for a device-private PMD. The subsequent !pmd_present() branch has a VM_BUG_ON() asserting migration is the only allowed non-present case; a device-private PMD trips it. Potential trigger: an HMM-based GPU driver races with madvise(MADV_COLD)/MADV_PAGEOUT: pmd_trans_huge(*pmd) reads true, then migrate_vma_pages() flips the PMD to a device-private entry before the PMD lock is acquired. Skip device-private PMDs after taking the lock, before the !pmd_present() check. Reported-by: sashiko-bot Link: https://sashiko.dev/#/patchset/20260703173903.3789516-1-usama.arif%40linux.dev?part=6 Fixes: 368076f52ebe ("mm/huge_memory: add device-private THP support to PMD operations") Signed-off-by: Usama Arif --- mm/madvise.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index 9292f60b19aa..870be398c6f3 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -384,6 +384,9 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, return 0; orig_pmd = *pmd; + if (pmd_is_device_private_entry(orig_pmd)) + goto huge_unlock; + if (is_huge_zero_pmd(orig_pmd)) goto huge_unlock; -- 2.53.0-Meta