After memory hot remove it seems we do not synchronize pgds for kernel virtual memory range (on vmemmap_free()). This seems bogus to me as it means we are left with stall entry for process with mm != mm_init Yet i am puzzle by the fact that i am only now hitting this issue. It never was an issue with 4.12 or before ie HMM never triggered following BUG_ON inside sync_global_pgds(): if (!p4d_none(*p4d_ref) && !p4d_none(*p4d)) BUG_ON(p4d_page_vaddr(*p4d) != p4d_page_vaddr(*p4d_ref)); It seems that Kirill 5 level page table changes play a role in this behavior change. I could not bisect because HMM is painfull to rebase for each bisection step so that is just my best guess. Am i missing something here ? Am i wrong in assuming that should sync pgd on vmemmap_free() ? If so anyone have a good guess on why i am now seeing the above BUG_ON ? Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Jérôme Glisse (1): x86/mm: synchronize pgd in vmemmap_free() arch/x86/mm/init_64.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) -- 2.4.11 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
