Re: [v2 PATCH 3/3] mm: hwpoison: dump page for unhandlable page

[Yang Shi]

On Wed, Sep 22, 2021 at 12:37 PM Luck, Tony <tony.luck@xxxxxxxxx> wrote:
>
> On Wed, Aug 18, 2021 at 10:41:16PM -0700, Yang Shi wrote:
> > Currently just very simple message is shown for unhandlable page, e.g.
> > non-LRU page, like:
> > soft_offline: 0x1469f2: unknown non LRU page type 5ffff0000000000 ()
> >
> > It is not very helpful for further debug, calling dump_page() could show
> > more useful information.
>
> Looks like your code already caught something. An error injection
> test may have injected into a shared library. Though I'm not sure that
> the refcount/mapcount in the dump agrees with that diagnosis from the
> author of this test.

The messages from dump_page() are (unwind them from mce logs):

[ 4817.630520] page:000000003ab9dca4 refcount:1 mapcount:0
mapping:0000000000000000 index:0x0 pfn:0xcef2747
[ 4817.646860] flags:
0x57ffffc0801000(reserved|hwpoison|node=1|zone=2|lastcpupid=0x1fffff)
[ 4818.033689] raw: 0057ffffc0801000 ffd400033bc9d1c8 ffd400033bc9d1c8
0000000000000000
[ 4818.280640] raw: 0000000000000000 0000000000000000 00000001ffffffff
0000000000000000

The page flags tell it is a "reserved" page and mapping is NULL. It
doesn't seem like a user page or movable page, so hwpoision can't
handle it so that the messages are dumped.

>
> Here's what appeared on the console:
>
> [ 4817.622254] mce: Uncorrected hardware memory error in user-access at cef2747000
> [ 4817.630520] page:000000003ab9dca4 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xcef2747
> [ 4817.638651] mce: Uncorrected hardware memory error in user-access at cef2747000
> [ 4817.646860] flags: 0x57ffffc0801000(reserved|hwpoison|node=1|zone=2|lastcpupid=0x1fffff)
> [ 4818.025515] mce: Uncorrected hardware memory error in user-access at cef2747000
> [ 4818.033689] raw: 0057ffffc0801000 ffd400033bc9d1c8 ffd400033bc9d1c8 0000000000000000
> [ 4818.272435] mce: Uncorrected hardware memory error in user-access at cef2747000
> [ 4818.280640] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
> [ 4818.280658] mce: Uncorrected hardware memory error in user-access at cef2747000
> [ 4818.313606] mce: Uncorrected hardware memory error in user-access at cef2747000
> [ 4818.321804] page dumped because: hwpoison: unhandlable page
> [ 4818.564802] mce: Uncorrected hardware memory error in user-access at cef2747000
> [ 4818.573043] Memory failure: 0xcef2747: recovery action for unknown page: Ignored
> [ 4818.595837] Memory failure: 0xcef2747: already hardware poisoned
> [ 4818.603245] Memory failure: 0xcef2747: Sending SIGBUS to multichase:67460 due to hardware memory corruption
> [ 4818.614297] Memory failure: 0xcef2747: already hardware poisoned
>
> -Tony