Re: [PATCH] powerpc/64s: fix hash page fault interrupt handler

On 29-Jun-2021, at 7:20 AM, Nicholas Piggin [off-list ref] wrote:

The early bad fault or key fault test in do_hash_fault() ends up calling
into ___do_page_fault without having gone through an interrupt handler
wrapper (except the initial _RAW one). This can end up calling local irq
functions while the interrupt has not been reconciled, which will likely
cause crashes and it trips up on a later patch that adds more assertions.

pkey_exec_prot from selftests causes this path to be executed.

There is no real reason to run the in_nmi() test should be performed
before the key fault check. In fact if a perf interrupt in the hash
fault code did a stack walk that was made to take a key fault somehow
then running ___do_page_fault could possibly cause another hash fault
causing problems. Move the in_nmi() test first, and then do everything
else inside the regular interrupt handler function.

Fixes: 3a96570ffceb ("powerpc: convert interrupt handlers to use wrappers")
Reported-by: Sachin Sant <redacted>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
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Thanks Nick. 
Fixes the reported problem.

Tested-by: Sachin Sant <redacted>

-Sachin