On Mon, Oct 04, 2021 at 01:55:30PM +0200, David Hildenbrand wrote: > On 04.10.21 13:50, Naoya Horiguchi wrote: > > From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> > > > > A hwpoison entry is a non-present page table entry to report > > memory error events to userspace. If we have an easy way to know > > which processes have hwpoison entries, that might be useful for > > user processes to take proper actions. But we don't have it now. > > So make pagemap interface expose hwpoison entries to userspace. > > Noting that this is only a way to inspect hwpoison set for private anonymous > memory. You cannot really identify anything related to shared memory. > > Do you also handle private hugetlb pages? I think yes. As long as hugepages are mmap()ed, we should be able to identify them with hwpoison entry (even if used via private/shared mapping). > > > > > Hwpoison entry for hugepage is also exposed by this patch. The below > > example shows how pagemap is visible in the case where a memory error > > hit a hugepage mapped to a process. > > > > $ ./page-types --no-summary --pid $PID --raw --list --addr 0x700000000+0x400 > > voffset offset len flags > > 700000000 12fa00 1 ___U_______Ma__H_G_________________f_______1 > > 700000001 12fa01 1ff ___________Ma___TG_________________f_______1 > > 700000200 12f800 1 __________B________X_______________f______w_ > > 700000201 12f801 1 ___________________X_______________f______w_ // memory failure hit this page > > 700000202 12f802 1fe __________B________X_______________f______w_ > > > > The entries with both of "X" flag (hwpoison flag) and "w" flag (swap > > flag) are considered as hwpoison entries. So all pages in 2MB range > > are inaccessible from the process. We can get actual error location > > by page-types in physical address mode. > > > > $ ./page-types --no-summary --addr 0x12f800+0x200 --raw --list > > offset len flags > > 12f800 1 __________B_________________________________ > > 12f801 1 ___________________X________________________ > > 12f802 1fe __________B_________________________________ > > > > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> > > --- > > fs/proc/task_mmu.c | 41 ++++++++++++++++++++++++++++++++--------- > > include/linux/swapops.h | 13 +++++++++++++ > > tools/vm/page-types.c | 7 ++++++- > > 3 files changed, 51 insertions(+), 10 deletions(-) > > > Please also update the documentation located at > > Documentation/admin-guide/mm/pagemap.rst I will do this in the next post. Thanks, Naoya Horigcuhi
