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From: James Clark <>
Cc: James Clark <>,
	Mark Rutland <>, Al Grant <>,
	John Garry <>,
	Suzuki K Poulose <>,
	Mathieu Poirier <>,
	Catalin Marinas <>
Subject: [PATCH v2] drivers/perf: Enable PID_IN_CONTEXTIDR with SPE
Date: Mon, 14 Dec 2020 10:45:02 +0200	[thread overview]
Message-ID: <> (raw)

Enable PID_IN_CONTEXTIDR by default when Arm SPE is enabled.
This flag is required to get PID data in the SPE trace. Without
it the perf tool will report 0 for PID which isn't very useful,
especially when doing system wide profiling or profiling
applications that fork.

There is a small performance overhead when enabling
PID_IN_CONTEXTIDR, but SPE itself is optional and not enabled by
default so the impact is minimised.

Cc: Will Deacon <>
Cc: Mark Rutland <>
Cc: Al Grant <>
Cc: Leo Yan <>
Cc: John Garry <>
Cc: Suzuki K Poulose <>
Cc: Mathieu Poirier <>
Cc: Catalin Marinas <>
Signed-off-by: James Clark <>
 arch/arm64/Kconfig.debug | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 265c4461031f..b030bb21a0bb 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -2,6 +2,7 @@
 	bool "Write the current PID to the CONTEXTIDR register"
+	default y if ARM_SPE_PMU
 	  Enabling this option causes the kernel to write the current PID to
 	  the CONTEXTIDR register, at the expense of some additional

             reply	other threads:[~2020-12-14  8:46 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-14  8:45 James Clark [this message]
2021-01-06 10:24 ` [PATCH v2] drivers/perf: Enable PID_IN_CONTEXTIDR with SPE Mark Rutland
2021-01-07 18:00   ` Al Grant

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