[PATCH 1/3] perf: arm_spe: Add barrier before enabling profiling buffer

[James Clark]

DEN0154 states that PMBPTR_EL1 must not be modified while the profiling
buffer is enabled. Ensure that enabling the buffer comes after setting
PMBPTR_EL1 by inserting an isb().

This only applies to guests for now, but in future versions of the
architecture the PE will be allowed to behave in the same way.

Fixes: d5d9696b0380 ("drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension")
Signed-off-by: James Clark <james.clark at linaro.org>
---
 drivers/perf/arm_spe_pmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index 3efed8839a4e..6235ca7ecd48 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -537,6 +537,7 @@ static void arm_spe_perf_aux_output_begin(struct perf_output_handle *handle,
 	limit += (u64)buf->base;
 	base = (u64)buf->base + PERF_IDX2OFF(handle->head, buf);
 	write_sysreg_s(base, SYS_PMBPTR_EL1);
+	isb();
 
 out_write_limit:
 	write_sysreg_s(limit, SYS_PMBLIMITR_EL1);

-- 
2.34.1