** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Cosmic)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Cosmic)
Status: New => Confirmed
** Changed in: linux (Ubuntu Cosmic)
Importance: Undecided => High
** Changed in: linux (Ubuntu Cosmic)
Assignee: (unassigned) => Thadeu Lima de Souza Cascardo (cascardo)
** Changed in: linux (Ubuntu Cosmic)
Status: Confirmed => In Progress
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https://bugs.launchpad.net/bugs/1774366
Title:
Fix MCE handling for user access of poisoned device-dax mapping
Status in intel:
Triaged
Status in linux package in Ubuntu:
In Progress
Status in linux source package in Cosmic:
In Progress
Bug description:
Description:
Customer reports:
—
We've tried the ndctl error injection. Now the error injection is
successful. But we have a couple of questions related with the
poisoned block.
Here are some tests/steps that I did:
1. I mmap the first 10GB of /dev/dax13.0 to virtual address space and
inject an error at offset 1GB (block offset should be 1GB/512bytes =
2097152) which seems fine:
[root@scaqae09celadm13 wning]# ndctl inject-error --uninject --block=2097152
--count=1 namespace13.0
Warning: Un-injecting previously injected errors here will
not cause the kernel to 'forget' its badblock entries. Those
have to be cleared through the normal process of writing
the affected blocks
{
"dev":"namespace13.0",
"mode":"dax",
"size":518967525376,
"uuid":"0738c8bd-3b3f-4989-9d0e-0e9c6006c810",
"chardev":"dax13.0",
"numa_node":0,
"badblock_count":1,
"badblocks":[
{ "offset":2097152, "length":1, "dimms":[ "nmem1" ] }
]
}
2. In my test program, I just try to read every address of the first
10GB. At the first time, when I read the offset 1GB, I got the SIGBUS
error, but in the sinfo struct of signal handler, the failed address
is NULL and signal code is 128 which seems incorrect. But then if we
run again, the unit test gets stuck here:
rt_sigaction(SIGBUS,
{0x400dd2, [], SA_RESTORER|SA_SIGINFO, 0x7fb5cf839270}
, NULL, 8) = 0
And here is the output of log messages:
Apr 3 14:39:23 scaqae09celadm13 kernel: mce: Uncorrected hardware memory
error in user-access at 952b200000
Apr 3 14:51:11 scaqae09celadm13 kernel: mce: Uncorrected hardware memory
error in user-access at 94eb300000
Apr 3 14:51:11 scaqae09celadm13 kernel: mce_notify_irq: 48 callbacks
suppressed
Apr 3 14:51:11 scaqae09celadm13 kernel: mce: [Hardware Error]: Machine check
events logged
Apr 3 14:51:11 scaqae09celadm13 kernel: Memory failure: 0x94eb300: reserved
kernel page still referenced by 1 users
Apr 3 14:51:11 scaqae09celadm13 kernel: Memory failure: 0x94eb300: recovery
action for reserved kernel page: Failed
Apr 3 14:51:11 scaqae09celadm13 kernel: mce: Memory error not recovered
The program I use is (simple do memcpy and directly read from the
target address):
for (i = 0; i < DAX_MAPPING_SIZE; i++) // DAX_MAPPING_SIZE is 10G
{ total += peek(buf + i); }
char peek(void *addr)
{ char temp[128]; memcpy(temp, addr, 1); return *(char *)addr; }
May I ask do we missed steps in triggering the SIGBUS error?
Target Kernel: 4.19
Target Release: 18.10
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