linux-kernel - [tip: x86/cache] x86/resctrl: Check monitoring static key in the MBM overflow handler

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Message-ID: <157928649703.396.16058225567355678427.tip-bot2@tip-bot2>
Date:   Fri, 17 Jan 2020 18:41:37 -0000
From:   "tip-bot2 for Xiaochen Shen" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Xiaochen Shen <xiaochen.shen@...el.com>,
        Borislav Petkov <bp@...e.de>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/cache] x86/resctrl: Check monitoring static key in the MBM
 overflow handler

The following commit has been merged into the x86/cache branch of tip:

Commit-ID:     536a0d8e79fb928f2735db37dda95682b6754f9a
Gitweb:        https://git.kernel.org/tip/536a0d8e79fb928f2735db37dda95682b6754f9a
Author:        Xiaochen Shen <xiaochen.shen@...el.com>
AuthorDate:    Thu, 12 Dec 2019 04:05:05 +08:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Fri, 17 Jan 2020 19:32:32 +01:00

x86/resctrl: Check monitoring static key in the MBM overflow handler

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@...el.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/1576094705-13660-1-git-send-email-xiaochen.shen@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 e49b772..181c992 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 397206f..773124b 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;