[PATCH v2 3/6] arm64: perf: Only advertise cap_user_time for arch_timer

[Leo Yan <leo.yan@linaro.org>]

From: Peter Zijlstra <peterz@infradead.org>

When sched_clock is running on anything other than arch_timer, don't
advertise cap_user_time*.

Requested-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/arm64/kernel/perf_event.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 35c2c737d4af..76f6afd28b48 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -13,6 +13,8 @@
 #include <asm/sysreg.h>
 #include <asm/virt.h>
 
+#include <clocksource/arm_arch_timer.h>
+
 #include <linux/acpi.h>
 #include <linux/clocksource.h>
 #include <linux/kvm_host.h>
@@ -1170,16 +1172,15 @@ void arch_perf_update_userpage(struct perf_event *event,
 	unsigned int seq;
 	u64 quot, rem, ns;
 
-	/*
-	 * Internal timekeeping for enabled/running/stopped times
-	 * is always computed with the sched_clock.
-	 */
-	userpg->cap_user_time = 1;
-	userpg->cap_user_time_zero = 1;
+	userpg->cap_user_time = 0;
+	userpg->cap_user_time_zero = 0;
 
 	do {
 		rd = sched_clock_read_begin(&seq);
 
+		if (rd->read_sched_clock != arch_timer_read_counter)
+			return;
+
 		userpg->time_mult = rd->mult;
 		userpg->time_shift = rd->shift;
 		userpg->time_zero = rd->epoch_ns;
@@ -1211,4 +1212,10 @@ void arch_perf_update_userpage(struct perf_event *event,
 		userpg->time_mult >>= 1;
 	}
 
+	/*
+	 * Internal timekeeping for enabled/running/stopped times
+	 * is always computed with the sched_clock.
+	 */
+	userpg->cap_user_time = 1;
+	userpg->cap_user_time_zero = 1;
 }
-- 
2.17.1