[lkml]   [2019]   [Dec]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 5.3 095/180] powerpc/perf: Disable trace_imc pmu
From: Madhavan Srinivasan <>

commit 249fad734a25889a4f23ed014d43634af6798063 upstream.

When a root user or a user with CAP_SYS_ADMIN privilege uses any
trace_imc performance monitoring unit events, to monitor application
or KVM threads, it may result in a checkstop (System crash).

The cause is frequent switching of the "trace/accumulation" mode of
the In-Memory Collection hardware (LDBAR).

This patch disables the trace_imc PMU unit entirely to avoid
triggering the checkstop. A future patch will reenable it at a later
stage once a workaround has been developed.

Fixes: 012ae244845f ("powerpc/perf: Trace imc PMU functions")
Cc: # v5.2+
Signed-off-by: Madhavan Srinivasan <>
Tested-by: Hariharan T.S. <>
[mpe: Add pr_info_once() so dmesg shows the PMU has been disabled]
Signed-off-by: Michael Ellerman <>
Signed-off-by: Greg Kroah-Hartman <>

arch/powerpc/platforms/powernv/opal-imc.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

--- a/arch/powerpc/platforms/powernv/opal-imc.c
+++ b/arch/powerpc/platforms/powernv/opal-imc.c
@@ -285,7 +285,14 @@ static int opal_imc_counters_probe(struc
- domain = IMC_DOMAIN_TRACE;
+ /*
+ * FIXME. Using trace_imc events to monitor application
+ * or KVM thread performance can cause a checkstop
+ * (system crash).
+ * Disable it for now.
+ */
+ pr_info_once("IMC: disabling trace_imc PMU\n");
+ domain = -1;
pr_warn("IMC Unknown Device type \n");

 \ /
  Last update: 2019-12-16 19:12    [W:0.320 / U:1.172 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site