From 249fad734a25889a4f23ed014d43634af6798063 Mon Sep 17 00:00:00 2001 From: Madhavan Srinivasan Date: Mon, 18 Nov 2019 09:14:52 +0530 Subject: 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 Tested-by: Hariharan T.S. [mpe: Add pr_info_once() so dmesg shows the PMU has been disabled] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20191118034452.9939-1-maddy@linux.vnet.ibm.com --- arch/powerpc/platforms/powernv/opal-imc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) 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"); -- cgit v1.2.3-59-g8ed1b