From: Aili Yao <yaoaili@xxxxxxxxxxxx>
When the page is already poisoned, another memory_failure() call in the
same page now returns 0, meaning OK. For nested memory mce handling, this
behavior may lead to one mce looping, Example:
1. When LCME is enabled, and there are two processes A && B running on
different core X && Y separately, which will access one same page, then
the page corrupted when process A access it, a MCE will be rasied to
core X and the error process is just underway.
2. Then B access the page and trigger another MCE to core Y, it will also
do error process, it will see TestSetPageHWPoison be true, and 0 is
returned.
3. The kill_me_maybe will check the return:
1244 static void kill_me_maybe(struct callback_head *cb)
1245 {
...
1254 if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags) &&
1255 !(p->mce_kflags & MCE_IN_KERNEL_COPYIN)) {
1256 set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
1257 sync_core();
1258 return;
1259 }
...
1267 }
4. The error process for B will end, and may nothing happened if
kill-early is not set, The process B will re-excute instruction and get
into mce again and then loop happens. And also the set_mce_nospec()
here is not proper, may refer to commit fd0e786d9d09 ("x86/mm,
mm/hwpoison: Don't unconditionally unmap kernel 1:1 pages").
For other cases which care the return value of memory_failure() should
check why they want to process a memory error which have already been
processed. This behavior seems reasonable.
Signed-off-by: Aili Yao <yaoaili@xxxxxxxxxxxx>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
---
mm/memory-failure.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git v5.12-rc8/mm/memory-failure.c v5.12-rc8_patched/mm/memory-failure.c
index 4087308e4b32..39d0ff0339b9 100644
--- v5.12-rc8/mm/memory-failure.c
+++ v5.12-rc8_patched/mm/memory-failure.c
@@ -1228,7 +1228,7 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
if (TestSetPageHWPoison(head)) {
pr_err("Memory failure: %#lx: already hardware poisoned\n",
pfn);
- return 0;
+ return -EHWPOISON;
}
num_poisoned_pages_inc();
@@ -1437,6 +1437,7 @@ int memory_failure(unsigned long pfn, int flags)
if (TestSetPageHWPoison(p)) {
pr_err("Memory failure: %#lx: already hardware poisoned\n",
pfn);
+ res = -EHWPOISON;
goto unlock_mutex;
}
--
2.25.1
