7fcbd9785d
pgoff should be aligned using ALIGN_DOWN() instead of ALIGN(). Otherwise,
vmf->address not aligned to fault_size will be aligned to the next
alignment, that can result in memory failure getting the wrong address.
It's a subtle situation that only can be observed in
page_mapped_in_vma() after the page is page fault handled by
dev_dax_huge_fault. Generally, there is little chance to perform
page_mapped_in_vma in dev-dax's page unless in specific error injection
to the dax device to trigger an MCE - memory-failure. In that case,
page_mapped_in_vma() will be triggered to determine which task is
accessing the failure address and kill that task in the end.
We used self-developed dax device (which is 2M aligned mapping) , to
perform error injection to random address. It turned out that error
injected to non-2M-aligned address was causing endless MCE until panic.
Because page_mapped_in_vma() kept resulting wrong address and the task
accessing the failure address was never killed properly:
[ 3783.719419] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3784.049006] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3784.049190] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3784.448042] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3784.448186] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3784.792026] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3784.792179] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3785.162502] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3785.162633] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3785.461116] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3785.461247] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3785.764730] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3785.764859] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3786.042128] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3786.042259] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3786.464293] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3786.464423] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3786.818090] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3786.818217] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
[ 3787.085297] mce: Uncorrected hardware memory error in user-access at
200c9742380
[ 3787.085424] Memory failure: 0x200c9742: recovery action for dax page:
Recovered
It took us several weeks to pinpoint this problem, but we eventually
used bpftrace to trace the page fault and mce address and successfully
identified the issue.
Joao added:
; Likely we never reproduce in production because we always pin
: device-dax regions in the region align they provide (Qemu does
: similarly with prealloc in hugetlb/file backed memory). I think this
: bug requires that we touch *unpinned* device-dax regions unaligned to
: the device-dax selected alignment (page size i.e. 4K/2M/1G)
Link: https://lkml.kernel.org/r/23c02a03e8d666fef11bbe13e85c69c8b4ca0624.1727421694.git.llfl@linux.alibaba.com
Fixes:
|
||
|---|---|---|
| .. | ||
| hmem | ||
| pmem | ||
| bus.c | ||
| bus.h | ||
| cxl.c | ||
| dax-private.h | ||
| device.c | ||
| Kconfig | ||
| kmem.c | ||
| Makefile | ||
| pmem.c | ||
| super.c | ||