From: Marcelo Tosatti <mtosatti@redhat.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>,
linux-kernel@vger.kernel.org, linux-hwmon@vger.kernel.org,
Frederic Weisbecker <frederic@kernel.org>
Subject: [PATCH v2] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs
Date: Fri, 16 Dec 2022 11:07:01 -0300 [thread overview]
Message-ID: <Y5x7hXGGLkcmejKq@tpad> (raw)
In-Reply-To: <68f76ac7-5edd-d437-8bef-e233f2876660@roeck-us.net>
The coretemp driver uses rdmsr_on_cpu calls to read
MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
which contain information about current core temperature.
For certain low latency applications, the RDMSR interruption exceeds
the applications requirements.
So disallow reading of crit_alarm and temp files via /sys, returning
-EINVAL, in case CPU isolation is enabled.
Temperature information from the housekeeping cores should be
sufficient to infer die temperature.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
v2: improve changelog to mention that an error is returned,
and sysfs file is not disabled (Guenter Roeck)
diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 9bee4d33fbdf..30a35f4130d5 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -27,6 +27,7 @@
#include <asm/msr.h>
#include <asm/processor.h>
#include <asm/cpu_device_id.h>
+#include <linux/sched/isolation.h>
#define DRVNAME "coretemp"
@@ -121,6 +122,10 @@ static ssize_t show_crit_alarm(struct device *dev,
struct platform_data *pdata = dev_get_drvdata(dev);
struct temp_data *tdata = pdata->core_data[attr->index];
+
+ if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
+ return -EINVAL;
+
mutex_lock(&tdata->update_lock);
rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
mutex_unlock(&tdata->update_lock);
@@ -158,6 +163,8 @@ static ssize_t show_temp(struct device *dev,
/* Check whether the time interval has elapsed */
if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
+ if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
+ return -EINVAL;
rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
/*
* Ignore the valid bit. In all observed cases the register
next prev parent reply other threads:[~2022-12-16 16:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-15 12:42 [PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs Marcelo Tosatti
2022-12-15 14:22 ` Guenter Roeck
2022-12-16 14:07 ` Marcelo Tosatti [this message]
2022-12-16 17:56 ` [PATCH v2] " Guenter Roeck
2022-12-16 20:24 ` [PATCH v3] " Marcelo Tosatti
2022-12-28 15:59 ` Guenter Roeck
2022-12-23 10:48 ` [PATCH] " Dan Carpenter
2022-12-26 12:43 ` Marcelo Tosatti
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