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powerpc/64s: Use relon prolog for EXC_VIRT_OOL_MASKABLE_HV handlers

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Hypervisor Virtualization and Directed Hypervisor Doorbell interrupt handlers
use the macro EXC_VIRT_OOL_MASKABLE_HV for their relocation-on handlers, which
calls MASKABLE_RELON_EXCEPTION_HV_OOL, which uses the *real mode* interrupt
prolog. This means we needlessly rfid from virtual mode to virtual mode.

For POWER8 it only affects doorbell IPIs. Context switch microbenchmark between
threads with snooze disabled (which causes IPI) gets about 3% faster, about 370
cycles. Should be more important on POWER9 with global doorbells and HVI for
host interrupts.

Use the RELON variant instead to reduce overhead.

Fixes: 1707dd1613 ("powerpc: Save CFAR before branching in interrupt entry paths")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Fold some more detail into the change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin 2017-04-13 19:45:48 +10:00 committed by Michael Ellerman
parent 686978b15c
commit a050d20d02
1 changed files with 1 additions and 1 deletions
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arch/powerpc/include/asm/exception-64s.h
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@ -522,7 +522,7 @@ END_FTR_SECTION_NESTED(ftr,ftr,943)
#define MASKABLE_RELON_EXCEPTION_HV_OOL(vec, label) \
EXCEPTION_PROLOG_1(PACA_EXGEN, SOFTEN_TEST_HV, vec); \
EXCEPTION_PROLOG_PSERIES_1(label, EXC_HV)
EXCEPTION_RELON_PROLOG_PSERIES_1(label, EXC_HV)
/*
* Our exception common code can be passed various "additions"