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?
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
--
Thanks,
David / dhildenb
