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authorMadhavan Srinivasan <maddy@linux.vnet.ibm.com>2019-11-18 09:14:52 +0530
committerMichael Ellerman <mpe@ellerman.id.au>2019-12-05 17:06:40 +1100
commit249fad734a25889a4f23ed014d43634af6798063 (patch)
treeaa148af2d2dde458e06d3dd42cbe393d6a39c387 /arch
parentpowerpc/powernv: Avoid re-registration of imc debugfs directory (diff)
downloadlinux-dev-249fad734a25889a4f23ed014d43634af6798063.tar.xz
linux-dev-249fad734a25889a4f23ed014d43634af6798063.zip
powerpc/perf: Disable trace_imc pmu
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: stable@vger.kernel.org # v5.2+ Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com> Tested-by: Hariharan T.S. <hari@linux.ibm.com> [mpe: Add pr_info_once() so dmesg shows the PMU has been disabled] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20191118034452.9939-1-maddy@linux.vnet.ibm.com
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/platforms/powernv/opal-imc.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
index 3b4518f4b643..000b350d4060 100644
--- a/arch/powerpc/platforms/powernv/opal-imc.c
+++ b/arch/powerpc/platforms/powernv/opal-imc.c
@@ -278,7 +278,14 @@ static int opal_imc_counters_probe(struct platform_device *pdev)
domain = IMC_DOMAIN_THREAD;
break;
case IMC_TYPE_TRACE:
- 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;
break;
default:
pr_warn("IMC Unknown Device type \n");