Subject: [PATCH v2] powerpc/perf: Disable trace_imc pmu

From: Madhavan Srinivasan <[email-masked]>
Date: Mon, 18 Nov 2019 09:14:52 +0530

When a root user or a user with CAP_SYS_ADMIN
privilege use trace_imc performance monitoring
unit events, to monitor application or KVM threads,
may result in a checkstop (System crash). Reason
being frequent switch of the "trace/accumulation"
mode of In-Memory Collection hardware.
This patch disables trace_imc pmu unit, but will
be re-enabled at a later stage with a fix patchset.

Fixes: 012ae244845f1 ('powerpc/perf: Trace imc PMU functions') 
Signed-off-by: Madhavan Srinivasan <[email-masked]>
---
Changelog v1:
- Added fixes and signed-off by.
 arch/powerpc/platforms/powernv/opal-imc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
index e04b20625cb9..5790f078771f 100644
--- a/arch/powerpc/platforms/powernv/opal-imc.c
+++ b/arch/powerpc/platforms/powernv/opal-imc.c
@@ -285,7 +285,12 @@ static int opal_imc_counters_probe(struct platform_device *pdev)
 			domain = IMC_DOMAIN_THREAD;
 			break;
 		case IMC_TYPE_TRACE:
-			domain = IMC_DOMAIN_TRACE;
+			/* Using trace_imc events to monitor
+			 * application or KVM thread performances
+			 * may result in a checkstop (system crash).
+			 * So disabling it for now.
+			 */
+			domain = -1;
 			break;
 		default:
 			pr_warn("IMC Unknown Device type \n");
-- 
2.21.0