On Wed, Aug 22, 2018 at 10:19:02AM +0200, Christophe LEROY wrote:

Le 21/08/2018 a 19:50, Ram Pai a ecrit :

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On Tue, Aug 21, 2018 at 04:40:15PM +1000, Michael Ellerman wrote:

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Christophe LEROY [off-list ref] writes:
...

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And I bisected its disappearance with commit 99cd1302327a2 ("powerpc:
Deliver SEGV signal on pkey violation")

Whoa that's weird.

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Looking at those two commits, especially the one which makes it
dissapear, I'm quite sceptic. Any idea on what could be the cause and/or
how to investigate further ?

Are you sure it's not some corruption that just happens to be masked by
that commit? I can't see anything in that commit that could explain that
change in behaviour.

The only real change is if you're hitting DSISR_KEYFAULT isn't it?

even with the 'commit 99cd1302327a2', a SEGV signal should get generated;
which should kill the process. Unless the process handles SEGV signals
with SEGV_PKUERR differently.

No, the sigsegv are not handled differently. And the trace shown it
is SEGV_MAPERR which is generated.

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The other surprising thing is, why is DSISR_KEYFAULT getting generated
in the first place?  Are keys somehow getting programmed into the HPTE?

Can't be that, because DSISR_KEYFAULT is filtered out when applying
DSISR_SRR1_MATCH_32S mask.

Ah.. in that case, 99cd1302327a2 does nothing to fix the problem.

Are you sure it is this patch that fixes the problem?


RP