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From:   Xiaochen Shen <xiaochen.shen@intel.com>
To:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
        tony.luck@intel.com, fenghua.yu@intel.com,
        reinette.chatre@intel.com
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org, pei.p.jia@intel.com,
        xiaochen.shen@intel.com
Subject: [PATCH] x86/resctrl: Check monitoring static key in MBM overflow handler
Date:   Thu, 12 Dec 2019 01:41:43 +0800
Message-Id: <1576086103-11640-1-git-send-email-xiaochen.shen@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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

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

MBM is a monitoring feature. MBM overflow handler intends to check if
monitoring feature is not enabled for fast return. So the accurate check
here is to check rdt_mon_enable_key instead of rdt_enable_key.

Fixes: e33026831bdb ("x86/intel_rdt/mbm: Handle counter overflow")
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
---
 arch/x86/kernel/cpu/resctrl/internal.h | 1 +
 arch/x86/kernel/cpu/resctrl/monitor.c  | 4 ++--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index e49b77283924..181c992f448c 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -57,6 +57,7 @@ static inline struct rdt_fs_context *rdt_fc2context(struct fs_context *fc)
 }
 
 DECLARE_STATIC_KEY_FALSE(rdt_enable_key);
+DECLARE_STATIC_KEY_FALSE(rdt_mon_enable_key);
 
 /**
  * struct mon_evt - Entry in the event list of a resource
diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
index 397206f23d14..773124b0e18a 100644
--- a/arch/x86/kernel/cpu/resctrl/monitor.c
+++ b/arch/x86/kernel/cpu/resctrl/monitor.c
@@ -514,7 +514,7 @@ void mbm_handle_overflow(struct work_struct *work)
 
 	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]);
@@ -543,7 +543,7 @@ void mbm_setup_overflow_handler(struct rdt_domain *dom, unsigned long delay_ms)
 	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;
-- 
1.8.3.1