[PATCH 5.4 134/152] x86/resctrl: Check monitoring static key in the MBM overflow handler

Greg Kroah-Hartman
2020-03-03T17:58:39Z

From: Xiaochen Shen <xiaochen.shen@intel.com>

commit 536a0d8e79fb928f2735db37dda95682b6754f9a upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kernel/cpu/resctrl/internal.h | 1 +
arch/x86/kernel/cpu/resctrl/monitor.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)

--- 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
}

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
--- 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_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]);
@@ -543,7 +543,7 @@ 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;