arm64: perf: don't expose CHAIN event in sysfs

The CHAIN event allows two 32-bit counters to be treated as a single
64-bit counter, under certain allocation restrictions on the PMU.

Whilst userspace could theoretically create CHAIN events using the raw
event syntax, we don't really want to advertise this in sysfs, since
it's useless in isolation. This patch removes the event from our /sys
entries.

Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index ca6beb10b592373f5e2bab7cde5c46b30ae604fa..838ccf123307df40b97f776ba82fa1b7e8182b25 100644 (file)
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -416,7 +416,7 @@ ARMV8_EVENT_ATTR(memory_error, ARMV8_PMUV3_PERFCTR_MEMORY_ERROR);
 ARMV8_EVENT_ATTR(inst_spec, ARMV8_PMUV3_PERFCTR_INST_SPEC);
 ARMV8_EVENT_ATTR(ttbr_write_retired, ARMV8_PMUV3_PERFCTR_TTBR_WRITE_RETIRED);
 ARMV8_EVENT_ATTR(bus_cycles, ARMV8_PMUV3_PERFCTR_BUS_CYCLES);
-ARMV8_EVENT_ATTR(chain, ARMV8_PMUV3_PERFCTR_CHAIN);
+/* Don't expose the chain event in /sys, since it's useless in isolation */
 ARMV8_EVENT_ATTR(l1d_cache_allocate, ARMV8_PMUV3_PERFCTR_L1D_CACHE_ALLOCATE);
 ARMV8_EVENT_ATTR(l2d_cache_allocate, ARMV8_PMUV3_PERFCTR_L2D_CACHE_ALLOCATE);
 ARMV8_EVENT_ATTR(br_retired, ARMV8_PMUV3_PERFCTR_BR_RETIRED);
@@ -467,7 +467,6 @@ static struct attribute *armv8_pmuv3_event_attrs[] = {
        &armv8_event_attr_inst_spec.attr.attr,
        &armv8_event_attr_ttbr_write_retired.attr.attr,
        &armv8_event_attr_bus_cycles.attr.attr,
-       &armv8_event_attr_chain.attr.attr,
        &armv8_event_attr_l1d_cache_allocate.attr.attr,
        &armv8_event_attr_l2d_cache_allocate.attr.attr,
        &armv8_event_attr_br_retired.attr.attr,