powerpc/64s/exception: Avoid touching the stack in hdecrementer

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The hdec interrupt handler is reported to sometimes fire in Linux if
KVM leaves it pending after a guest exists. This is harmless, so there
is a no-op handler for it.

The interrupt handler currently uses the regular kernel stack. Change
this to avoid touching the stack entirely.

This should be the last place where the regular Linux stack can be
accessed with asynchronous interrupts (including PMI) soft-masked.
It might be possible to take advantage of this invariant, e.g., to
context switch the kernel stack SLB entry without clearing MSR[EE].

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-17-npiggin@gmail.com

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Nicholas Piggin 2020-02-26 03:35:25 +10:00 • committed by Michael Ellerman

parent 9d598f9344

commit 2babd6ea43

3 changed files with 20 additions and 15 deletions

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1

arch/powerpc/include/asm/time.h

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25

arch/powerpc/kernel/exceptions-64s.S

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9

arch/powerpc/kernel/time.c

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