powerpc/perf: Avoid mutating event in power8_get_constraint()

We only need to mask the EBB bit out of the event for the check of the
special PMC 5 & 6 events. So use a local to do it just for that code,
rather than changing the event value for the life of the function.

While we're there move the set of mask and value after all the checks.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/perf/power8-pmu.c b/arch/powerpc/perf/power8-pmu.c
index 1d7c4428a55ebc49692856cc486ec16cb1d21bb5..67aab104b9fefb9f05b439b635f9cd50848c8402 100644 (file)
--- a/arch/powerpc/perf/power8-pmu.c
+++ b/arch/powerpc/perf/power8-pmu.c
@@ -270,18 +270,20 @@ static int power8_get_constraint(u64 event, unsigned long *maskp, unsigned long
        cache = (event >> EVENT_CACHE_SEL_SHIFT)  & EVENT_CACHE_SEL_MASK;
        ebb   = (event >> EVENT_EBB_SHIFT)        & EVENT_EBB_MASK;
 
-       /* Clear the EBB bit in the event, so event checks work below */
-       event &= ~(EVENT_EBB_MASK << EVENT_EBB_SHIFT);
-
        if (pmc) {
+               u64 base_event;
+
                if (pmc > 6)
                        return -1;
 
-               mask  |= CNST_PMC_MASK(pmc);
-               value |= CNST_PMC_VAL(pmc);
+               /* Ignore Linux defined bits when checking event below */
+               base_event = event & ~(EVENT_EBB_MASK << EVENT_EBB_SHIFT);
 
-               if (pmc >= 5 && event != 0x500fa && event != 0x600f4)
+               if (pmc >= 5 && base_event != 0x500fa && base_event != 0x600f4)
                        return -1;
+
+               mask  |= CNST_PMC_MASK(pmc);
+               value |= CNST_PMC_VAL(pmc);
        }
 
        if (pmc <= 4) {