From: Xiaochen Shen <xiaochen.shen@intel.com>
Date: Thu, 12 Dec 2019 04:05:05 +0800
Subject: x86/resctrl: Check monitoring static key in the MBM overflow handler
Git-commit: 536a0d8e79fb928f2735db37dda95682b6754f9a
Patch-mainline: v5.6-rc1
References: bsc#1114279

Currently, there are three static keys in the resctrl file system:
rdt_mon_enable_key and rdt_alloc_enable_key indicate if the monitoring
feature and the allocation feature are enabled, respectively. The
rdt_enable_key is enabled when either the monitoring feature or the
allocation feature is enabled.

If no monitoring feature is present (either hardware doesn't support a
monitoring feature or the feature is disabled by the kernel command line
option "rdt="), rdt_enable_key is still enabled but rdt_mon_enable_key
is disabled.

MBM is a monitoring feature. The MBM overflow handler intends to
check if the monitoring feature is not enabled for fast return.

So check the rdt_mon_enable_key in it instead of the rdt_enable_key as
former is the more accurate check.

 [ bp: Massage commit message. ]

Fixes: e33026831bdb ("x86/intel_rdt/mbm: Handle counter overflow")
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1576094705-13660-1-git-send-email-xiaochen.shen@intel.com
---
 arch/x86/kernel/cpu/intel_rdt_monitor.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -26,6 +26,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <asm/cpu_device_id.h>
+#include <asm/resctrl_sched.h>
 #include "internal.h"
 
 struct rmid_entry {
@@ -525,7 +526,7 @@ void mbm_handle_overflow(struct work_str
 
 	mutex_lock(&rdtgroup_mutex);
 
-	if (!static_branch_likely(&rdt_enable_key))
+	if (!static_branch_likely(&rdt_mon_enable_key))
 		goto out_unlock;
 
 	d = get_domain_from_cpu(cpu, &rdt_resources_all[RDT_RESOURCE_L3]);
@@ -554,7 +555,7 @@ void mbm_setup_overflow_handler(struct r
 	unsigned long delay = msecs_to_jiffies(delay_ms);
 	int cpu;
 
-	if (!static_branch_likely(&rdt_enable_key))
+	if (!static_branch_likely(&rdt_mon_enable_key))
 		return;
 	cpu = cpumask_any(&dom->cpu_mask);
 	dom->mbm_work_cpu = cpu;