| 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: <20251125045618.texoubmzmiz7cz6c@lcpd911>
Date: Tue, 25 Nov 2025 10:26:18 +0530
From: Dhruva Gole <d-gole@...com>
To: Ulf Hansson <ulf.hansson@...aro.org>
CC: "Rafael J . Wysocki" <rafael@...nel.org>, <linux-pm@...r.kernel.org>,
Vincent Guittot <vincent.guittot@...aro.org>, Peter Zijlstra
<peterz@...radead.org>, Kevin Hilman <khilman@...libre.com>, Pavel Machek
<pavel@...nel.org>, Len Brown <len.brown@...el.com>, Daniel Lezcano
<daniel.lezcano@...aro.org>, Maulik Shah <quic_mkshah@...cinc.com>, "Prasad
Sodagudi" <psodagud@...cinc.com>, Deepti Jaggi <quic_djaggi@...cinc.com>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/6] PM: QoS: Introduce a CPU system wakeup QoS limit
On Nov 21, 2025 at 11:03:07 +0100, Ulf Hansson wrote:
> Some platforms supports multiple low power states for CPUs that can be used
> when entering system-wide suspend. Currently we are always selecting the
> deepest possible state for the CPUs, which can break the system wakeup
> latency constraint that may be required for a use case.
>
> Let's take the first step towards addressing this problem, by introducing
> an interface for user space, that allows us to specify the CPU system
> wakeup QoS limit. Subsequent changes will start taking into account the new
> QoS limit.
>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> ---
>
> Changes in v3:
> - Add Kconfig for the new interface (Rafael).
> - Updated commit message.
>
> Changes in v2:
> - Renamings to reflect the QoS are limited to CPUs.
> - Move code inside "CONFIG_CPU_IDLE".
> ---
> include/linux/pm_qos.h | 9 ++++
> kernel/power/Kconfig | 4 ++
> kernel/power/qos.c | 106 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 119 insertions(+)
>
> diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
> index 4a69d4af3ff8..6cea4455f867 100644
> --- a/include/linux/pm_qos.h
> +++ b/include/linux/pm_qos.h
> @@ -162,6 +162,15 @@ static inline void cpu_latency_qos_update_request(struct pm_qos_request *req,
> static inline void cpu_latency_qos_remove_request(struct pm_qos_request *req) {}
> #endif
>
> +#ifdef CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP
> +s32 cpu_wakeup_latency_qos_limit(void);
> +#else
> +static inline s32 cpu_wakeup_latency_qos_limit(void)
> +{
> + return PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
> +}
> +#endif
> +
> #ifdef CONFIG_PM
> enum pm_qos_flags_status __dev_pm_qos_flags(struct device *dev, s32 mask);
> enum pm_qos_flags_status dev_pm_qos_flags(struct device *dev, s32 mask);
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 54a623680019..839e2dbb889e 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -202,6 +202,10 @@ config PM_WAKELOCKS_GC
> depends on PM_WAKELOCKS
> default y
>
> +config PM_QOS_CPU_SYSTEM_WAKEUP
> + bool "User space interface for CPU system wakeup QoS"
> + depends on CPU_IDLE
> +
I see that checkpatch complains here with a warning:
please write a help paragraph that fully describes the config symbol with at least 4 lines
I somewhat agree too, since it's a new and pretty important feature that
we're putting behind this config best to add some help around it.
With that,
Reviewed-by: Dhruva Gole <d-gole@...com>
> config PM
> bool "Device power management core functionality"
> help
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index 4244b069442e..f7d8064e9adc 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -415,6 +415,105 @@ static struct miscdevice cpu_latency_qos_miscdev = {
> .fops = &cpu_latency_qos_fops,
> };
>
> +#ifdef CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP
> +/* The CPU system wakeup latency QoS. */
> +static struct pm_qos_constraints cpu_wakeup_latency_constraints = {
> + .list = PLIST_HEAD_INIT(cpu_wakeup_latency_constraints.list),
> + .target_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT,
> + .default_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT,
> + .no_constraint_value = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT,
> + .type = PM_QOS_MIN,
> +};
> +
> +/**
> + * cpu_wakeup_latency_qos_limit - Current CPU system wakeup latency QoS limit.
> + *
> + * Returns the current CPU system wakeup latency QoS limit that may have been
> + * requested by user space.
> + */
> +s32 cpu_wakeup_latency_qos_limit(void)
> +{
> + return pm_qos_read_value(&cpu_wakeup_latency_constraints);
> +}
> +
> +static int cpu_wakeup_latency_qos_open(struct inode *inode, struct file *filp)
> +{
> + struct pm_qos_request *req;
> +
> + req = kzalloc(sizeof(*req), GFP_KERNEL);
> + if (!req)
> + return -ENOMEM;
> +
> + req->qos = &cpu_wakeup_latency_constraints;
> + pm_qos_update_target(req->qos, &req->node, PM_QOS_ADD_REQ,
> + PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
> + filp->private_data = req;
> +
> + return 0;
> +}
> +
> +static int cpu_wakeup_latency_qos_release(struct inode *inode,
> + struct file *filp)
> +{
> + struct pm_qos_request *req = filp->private_data;
> +
> + filp->private_data = NULL;
> + pm_qos_update_target(req->qos, &req->node, PM_QOS_REMOVE_REQ,
> + PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
> + kfree(req);
> +
> + return 0;
> +}
> +
> +static ssize_t cpu_wakeup_latency_qos_read(struct file *filp, char __user *buf,
> + size_t count, loff_t *f_pos)
> +{
> + s32 value = pm_qos_read_value(&cpu_wakeup_latency_constraints);
> +
> + return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
> +}
> +
> +static ssize_t cpu_wakeup_latency_qos_write(struct file *filp,
> + const char __user *buf,
> + size_t count, loff_t *f_pos)
> +{
> + struct pm_qos_request *req = filp->private_data;
> + s32 value;
> +
> + if (count == sizeof(s32)) {
> + if (copy_from_user(&value, buf, sizeof(s32)))
> + return -EFAULT;
> + } else {
> + int ret;
> +
> + ret = kstrtos32_from_user(buf, count, 16, &value);
> + if (ret)
> + return ret;
> + }
> +
> + if (value < 0)
> + return -EINVAL;
> +
> + pm_qos_update_target(req->qos, &req->node, PM_QOS_UPDATE_REQ, value);
> +
> + return count;
> +}
> +
> +static const struct file_operations cpu_wakeup_latency_qos_fops = {
> + .open = cpu_wakeup_latency_qos_open,
> + .release = cpu_wakeup_latency_qos_release,
> + .read = cpu_wakeup_latency_qos_read,
> + .write = cpu_wakeup_latency_qos_write,
> + .llseek = noop_llseek,
> +};
> +
> +static struct miscdevice cpu_wakeup_latency_qos_miscdev = {
> + .minor = MISC_DYNAMIC_MINOR,
> + .name = "cpu_wakeup_latency",
> + .fops = &cpu_wakeup_latency_qos_fops,
> +};
> +#endif /* CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP */
> +
> static int __init cpu_latency_qos_init(void)
> {
> int ret;
> @@ -424,6 +523,13 @@ static int __init cpu_latency_qos_init(void)
> pr_err("%s: %s setup failed\n", __func__,
> cpu_latency_qos_miscdev.name);
>
> +#ifdef CONFIG_PM_QOS_CPU_SYSTEM_WAKEUP
> + ret = misc_register(&cpu_wakeup_latency_qos_miscdev);
> + if (ret < 0)
> + pr_err("%s: %s setup failed\n", __func__,
> + cpu_wakeup_latency_qos_miscdev.name);
> +#endif
> +
--
Best regards,
Dhruva Gole
Texas Instruments Incorporated
Powered by blists - more mailing lists