powerpc/64s: Use relon prolog for EXC_VIRT_OOL_MASKABLE_HV handlers

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>

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 14752eee3d0c44816a61b395970186c1e56d4a21..b89c91e27dd0efb3853823c681638ecf7858a670 100644 (file)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -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"