| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <562A424B.2070108@roeck-us.net>
Date: Fri, 23 Oct 2015 07:20:59 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Huang Rui <ray.huang@....com>, Borislav Petkov <bp@...e.de>,
Peter Zijlstra <peterz@...radead.org>,
Jean Delvare <jdelvare@...e.de>,
Andy Lutomirski <luto@...capital.net>,
Andreas Herrmann <herrmann.der.user@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Len Brown <lenb@...nel.org>,
John Stultz <john.stultz@...aro.org>,
Frédéric Weisbecker <fweisbec@...il.com>
Cc: lm-sensors@...sensors.org, linux-kernel@...r.kernel.org,
x86@...nel.org,
Andreas Herrmann <herrmann.der.user@...glemail.com>,
Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
Borislav Petkov <bp@...en8.de>,
Fengguang Wu <fengguang.wu@...el.com>,
Aaron Lu <aaron.lu@...el.com>, Tony Li <tony.li@....com>
Subject: Re: [PATCH v2 07/10] hwmon: (fam15h_power) Introduce a cpu
accumulated power reporting algorithm
On 10/19/2015 07:28 PM, Huang Rui wrote:
> This patch introduces an algorithm that computes the average power by
> reading a delta value of “core power accumulator” register during
> measurement interval, and then dividing delta value by the length of
> the time interval.
>
> User is able to use power1_average entry to measure the processor power
> consumption and power1_average_interval entry to set the interval.
>
> A simple example:
>
> ray@...ub:~/tip$ sensors
> fam15h_power-pci-00c4
> Adapter: PCI adapter
> power1: 23.73 mW (avg = 634.63 mW, interval = 0.01 s)
> (crit = 15.00 W)
>
> ...
>
> The result is current average processor power consumption in 10
> millisecond. The unit of the result is uWatt.
>
> Suggested-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Huang Rui <ray.huang@....com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> ---
> drivers/hwmon/fam15h_power.c | 120 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 120 insertions(+)
>
> diff --git a/drivers/hwmon/fam15h_power.c b/drivers/hwmon/fam15h_power.c
> index 6321f73..a5a539e 100644
> --- a/drivers/hwmon/fam15h_power.c
> +++ b/drivers/hwmon/fam15h_power.c
> @@ -26,6 +26,9 @@
> #include <linux/pci.h>
> #include <linux/bitops.h>
> #include <linux/cpumask.h>
> +#include <linux/mutex.h>
> +#include <linux/time.h>
> +#include <linux/sched.h>
> #include <asm/processor.h>
> #include <asm/msr.h>
>
> @@ -64,6 +67,10 @@ struct fam15h_power_data {
> u64 cu_acc_power[MAX_CUS];
> /* performance timestamp counter */
> u64 cpu_sw_pwr_ptsc[MAX_CUS];
> + /* online/offline status of current compute unit */
> + int cu_on[MAX_CUS];
> + unsigned long power_period;
> + struct mutex acc_pwr_mutex;
Can you elaborate a bit about what this mutex is supposed to protect ?
To me it seems that it doesn't really protect anything.
> };
>
> static ssize_t show_power(struct device *dev,
> @@ -132,11 +139,15 @@ static void do_read_registers_on_cu(void *_data)
> cores_per_cu = amd_get_cores_per_cu();
> cu = cpu / cores_per_cu;
>
> + mutex_lock(&data->acc_pwr_mutex);
> WARN_ON(rdmsrl_safe(MSR_F15H_CU_PWR_ACCUMULATOR,
> &data->cu_acc_power[cu]));
>
> WARN_ON(rdmsrl_safe(MSR_F15H_PTSC,
> &data->cpu_sw_pwr_ptsc[cu]));
> +
> + data->cu_on[cu] = 1;
> + mutex_unlock(&data->acc_pwr_mutex);
... for example, while this protects cu_on[cu],
> }
>
> static int read_registers(struct fam15h_power_data *data)
> @@ -148,6 +159,10 @@ static int read_registers(struct fam15h_power_data *data)
> cores_per_cu = amd_get_cores_per_cu();
> cu_num = boot_cpu_data.x86_max_cores / cores_per_cu;
>
> + mutex_lock(&data->acc_pwr_mutex);
> + memset(data->cu_on, 0, sizeof(int) * MAX_CUS);
> + mutex_unlock(&data->acc_pwr_mutex);
... this code may well overwrite that same value.
> +
> WARN_ON_ONCE(cu_num > MAX_CUS);
>
> ret = zalloc_cpumask_var(&mask, GFP_KERNEL);
> @@ -184,18 +199,113 @@ static int read_registers(struct fam15h_power_data *data)
> return 0;
> }
>
> +static ssize_t acc_show_power(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct fam15h_power_data *data = dev_get_drvdata(dev);
> + u64 prev_cu_acc_power[MAX_CUS], prev_ptsc[MAX_CUS],
> + jdelta[MAX_CUS];
> + u64 tdelta, avg_acc;
> + int cu, cu_num, cores_per_cu, ret;
> + signed long leftover;
> +
> + cores_per_cu = amd_get_cores_per_cu();
> + cu_num = boot_cpu_data.x86_max_cores / cores_per_cu;
> +
> + ret = read_registers(data);
> + if (ret)
> + return 0;
> +
> + cu = 0;
> + while(cu++ < cu_num) {
> + prev_cu_acc_power[cu] = data->cu_acc_power[cu];
> + prev_ptsc[cu] = data->cpu_sw_pwr_ptsc[cu];
> + }
... and multiple parallel reads on the power attribute must produce
pretty random values, unless I am really missing something.
> +
> + leftover = schedule_timeout_interruptible(
> + msecs_to_jiffies(data->power_period)
> + );
> + if (leftover)
> + return 0;
> +
> + ret = read_registers(data);
> + if (ret)
> + return 0;
> +
With a 10ms period, I wonder how accurate this really is.
> + for (cu = 0, avg_acc = 0; cu < cu_num; cu++) {
> + /* check if current compute unit is online */
> + if (data->cu_on[cu] == 0)
> + continue;
> +
> + if (data->cu_acc_power[cu] < prev_cu_acc_power[cu]) {
> + jdelta[cu] = data->max_cu_acc_power + data->cu_acc_power[cu];
> + jdelta[cu] -= prev_cu_acc_power[cu];
> + } else {
> + jdelta[cu] = data->cu_acc_power[cu] - prev_cu_acc_power[cu];
> + }
> + tdelta = data->cpu_sw_pwr_ptsc[cu] - prev_ptsc[cu];
> + jdelta[cu] *= data->cpu_pwr_sample_ratio * 1000;
> + do_div(jdelta[cu], tdelta);
> +
> + /* the unit is microWatt */
> + avg_acc += jdelta[cu];
> + }
> +
> + return sprintf(buf, "%llu\n", (unsigned long long)avg_acc);
> +}
> +static DEVICE_ATTR(power1_average, S_IRUGO, acc_show_power, NULL);
> +
> +
> +static ssize_t acc_show_power_period(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct fam15h_power_data *data = dev_get_drvdata(dev);
> +
> + return sprintf(buf, "%lu\n", data->power_period);
> +}
> +
> +static ssize_t acc_set_power_period(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct fam15h_power_data *data = dev_get_drvdata(dev);
> + unsigned long temp;
> + int ret;
> +
> + ret = kstrtoul(buf, 10, &temp);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&data->acc_pwr_mutex);
> + data->power_period = temp;
> + mutex_unlock(&data->acc_pwr_mutex);
This doesn't really protect anything either except that power_period
can not be updated while the lock is active. But the code using
power_period does not run under mutex protection, so that seems pretty
pointless.
Also, this accepts an unlimited timeout. If I understand correctly,
setting the timeout to, say, 10 seconds will cause the read function
to hang for that period of time. Setting it to 1 hour will cause the read
function to hang for 1 hour.
Does this really make sense ?
> +
> + return count;
> +}
> +static DEVICE_ATTR(power1_average_interval, S_IRUGO | S_IWUSR,
> + acc_show_power_period, acc_set_power_period);
> +
> static int fam15h_power_init_attrs(struct pci_dev *pdev,
> struct fam15h_power_data *data)
> {
> int n = FAM15H_MIN_NUM_ATTRS;
> struct attribute **fam15h_power_attrs;
> struct cpuinfo_x86 *c = &boot_cpu_data;
> + u32 cpuid;
>
> if (c->x86 == 0x15 &&
> ((c->x86_model <= 0xf) ||
> (c->x86_model >= 0x60 && c->x86_model <= 0x6f)))
> n += 1;
>
> + cpuid = cpuid_edx(0x80000007);
> +
> + /* check if processor supports accumulated power */
> + if (cpuid & BIT(12))
> + n += 2;
> +
> fam15h_power_attrs = devm_kcalloc(&pdev->dev, n,
> sizeof(*fam15h_power_attrs),
> GFP_KERNEL);
> @@ -210,6 +320,11 @@ static int fam15h_power_init_attrs(struct pci_dev *pdev,
> (c->x86_model >= 0x60 && c->x86_model <= 0x6f)))
> fam15h_power_attrs[n++] = &dev_attr_power1_input.attr;
>
> + if (cpuid & BIT(12)) {
> + fam15h_power_attrs[n++] = &dev_attr_power1_average.attr;
> + fam15h_power_attrs[n++] = &dev_attr_power1_average_interval.attr;
> + }
> +
> data->fam15h_power_group.attrs = fam15h_power_attrs;
>
> return 0;
> @@ -322,6 +437,9 @@ static int fam15h_power_init_data(struct pci_dev *f4,
>
> data->max_cu_acc_power = tmp;
>
> + /* set default interval as 10 ms */
> + data->power_period = 10;
> +
> ret = read_registers(data);
>
> return ret;
> @@ -349,6 +467,8 @@ static int fam15h_power_probe(struct pci_dev *pdev,
> if (!data)
> return -ENOMEM;
>
> + mutex_init(&data->acc_pwr_mutex);
> +
> ret = fam15h_power_init_data(pdev, data);
> if (ret)
> return ret;
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists