From: Fenghua Yu <fenghua.yu@intel.com>
To: "Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>, "H Peter Anvin" <hpa@zytor.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Peter Zijlstra" <peterz@infradead.org>,
"Ashok Raj" <ashok.raj@intel.com>,
"Tony Luck" <tony.luck@intel.com>,
"Ravi V Shankar" <ravi.v.shankar@intel.com>
Cc: "linux-kernel" <linux-kernel@vger.kernel.org>,
"x86" <x86@kernel.org>, Fenghua Yu <fenghua.yu@intel.com>
Subject: [PATCH v5 4/5] x86/umwait: Add sysfs interface to control umwait maximum time
Date: Wed, 19 Jun 2019 18:33:57 -0700 [thread overview]
Message-ID: <1560994438-235698-5-git-send-email-fenghua.yu@intel.com> (raw)
In-Reply-To: <1560994438-235698-1-git-send-email-fenghua.yu@intel.com>
IA32_UMWAIT_CONTROL[31:2] determines the maximum time in TSC-quanta
that processor can stay in C0.1 or C0.2. A zero value means no maximum
time.
Each instruction sets its own deadline in the instruction's implicit
input EDX:EAX value. The instruction wakes up if the time-stamp counter
reaches or exceeds the specified deadline, or the umwait maximum time
expires, or a store happens in the monitored address range in umwait.
Users can write an unsigned 32-bit number to
/sys/devices/system/cpu/umwait_control/max_time to change the default
value. Note that a value of zero means there is no limit. Low order
two bits must be zero.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/umwait.c | 40 ++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/arch/x86/kernel/cpu/umwait.c b/arch/x86/kernel/cpu/umwait.c
index 3bd6d37a7b2c..4b2aff7b2d4d 100644
--- a/arch/x86/kernel/cpu/umwait.c
+++ b/arch/x86/kernel/cpu/umwait.c
@@ -126,8 +126,48 @@ static ssize_t enable_c02_store(struct device *dev,
}
static DEVICE_ATTR_RW(enable_c02);
+static ssize_t
+max_time_show(struct device *kobj, struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%u\n", get_umwait_ctrl_max_time());
+}
+
+static ssize_t max_time_store(struct device *kobj,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ u32 max_time;
+ int ret;
+
+ ret = kstrtou32(buf, 0, &max_time);
+ if (ret)
+ return ret;
+
+ /* bits[1:0] must be zero */
+ if (max_time & ~MSR_IA32_UMWAIT_CONTROL_MAX_TIME)
+ return -EINVAL;
+
+ mutex_lock(&umwait_lock);
+
+ if (max_time == get_umwait_ctrl_max_time())
+ goto out_unlock;
+
+ WRITE_ONCE(umwait_control_cached,
+ UMWAIT_CTRL_VAL(max_time, get_umwait_ctrl_c02()));
+
+ /* Update umwait max time on all CPUs */
+ on_each_cpu(umwait_control_msr_update, NULL, 1);
+
+out_unlock:
+ mutex_unlock(&umwait_lock);
+
+ return count;
+}
+static DEVICE_ATTR_RW(max_time);
+
static struct attribute *umwait_attrs[] = {
&dev_attr_enable_c02.attr,
+ &dev_attr_max_time.attr,
NULL
};
--
2.19.1
next prev parent reply other threads:[~2019-06-20 1:44 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-20 1:33 [PATCH v5 0/5] x86/umwait: Enable user wait instructions Fenghua Yu
2019-06-20 1:33 ` [PATCH v5 1/5] x86/cpufeatures: Enumerate " Fenghua Yu
2019-06-24 0:01 ` [tip:x86/cpu] " tip-bot for Fenghua Yu
2019-06-20 1:33 ` [PATCH v5 2/5] x86/umwait: Initialize umwait control values Fenghua Yu
2019-06-23 22:39 ` Thomas Gleixner
2019-06-24 22:12 ` Fenghua Yu
2019-06-24 0:01 ` [tip:x86/cpu] " tip-bot for Fenghua Yu
2019-06-20 1:33 ` [PATCH v5 3/5] x86/umwait: Add sysfs interface to control umwait C0.2 state Fenghua Yu
2019-06-23 22:40 ` Thomas Gleixner
2019-06-24 0:02 ` [tip:x86/cpu] " tip-bot for Fenghua Yu
2019-06-20 1:33 ` Fenghua Yu [this message]
2019-06-23 22:40 ` [PATCH v5 4/5] x86/umwait: Add sysfs interface to control umwait maximum time Thomas Gleixner
2019-06-24 0:03 ` [tip:x86/cpu] " tip-bot for Fenghua Yu
2019-06-20 1:33 ` [PATCH v5 5/5] x86/umwait: Document umwait control sysfs interfaces Fenghua Yu
2019-06-23 22:42 ` Thomas Gleixner
2019-06-23 22:46 ` Thomas Gleixner
2019-06-24 0:03 ` [tip:x86/cpu] Documentation/ABI: " tip-bot for Fenghua Yu
2019-06-20 16:25 ` [PATCH v5 0/5] x86/umwait: Enable user wait instructions Andy Lutomirski
2019-06-20 23:28 ` Fenghua Yu
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