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 <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Mel Gorman <[email protected]> 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
