| 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: <2ce31807-bf89-4c79-82d0-31a5cda2a6a5@nvidia.com>
Date: Sun, 25 Jan 2026 02:02:22 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: Pierre Gondois <pierre.gondois@....com>, rafael@...nel.org,
viresh.kumar@...aro.org, zhenglifeng1@...wei.com, ionela.voinescu@....com,
lenb@...nel.org, robert.moore@...el.com, corbet@....net,
rdunlap@...radead.org, ray.huang@....com, gautham.shenoy@....com,
mario.limonciello@....com, perry.yuan@....com, zhanjie9@...ilicon.com,
linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
linux-doc@...r.kernel.org, acpica-devel@...ts.linux.dev,
linux-kernel@...r.kernel.org
Cc: linux-tegra@...r.kernel.org, treding@...dia.com, jonathanh@...dia.com,
vsethi@...dia.com, ksitaraman@...dia.com, sanjayc@...dia.com,
nhartman@...dia.com, bbasu@...dia.com, sumitg@...dia.com
Subject: Re: [PATCH v6 6/9] ACPI: CPPC: add APIs and sysfs interface for
min/max_perf
On 22/01/26 17:06, Pierre Gondois wrote:
> External email: Use caution opening links or attachments
>
>
> On 1/20/26 15:56, Sumit Gupta wrote:
>> Add cppc_get/set_min_perf() and cppc_get/set_max_perf() APIs to read and
>> write the MIN_PERF and MAX_PERF registers.
>>
>> Also add sysfs interfaces (min_perf, max_perf) in cppc_cpufreq driver
>> to expose these controls to userspace. The sysfs values are in frequency
>> (kHz) for consistency with other cpufreq sysfs files.
>>
>> A mutex is used to serialize sysfs store operations to ensure hardware
>> register writes and perf_ctrls updates are atomic.
>>
>> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
>> ---
>> drivers/acpi/cppc_acpi.c | 44 +++++++++
>> drivers/cpufreq/cppc_cpufreq.c | 157 +++++++++++++++++++++++++++++++++
>> include/acpi/cppc_acpi.h | 20 +++++
>> 3 files changed, 221 insertions(+)
>>
>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
>> index 45c6bd6ec24b..46bf45f8b0f3 100644
>> --- a/drivers/acpi/cppc_acpi.c
>> +++ b/drivers/acpi/cppc_acpi.c
>> @@ -1743,6 +1743,50 @@ int cppc_set_auto_sel(int cpu, bool enable)
>> }
>> EXPORT_SYMBOL_GPL(cppc_set_auto_sel);
>>
>> +/**
>> + * cppc_get_min_perf - Read minimum performance register.
>> + * @cpu: CPU from which to read register.
>> + * @min_perf: Return address.
>> + */
>> +int cppc_get_min_perf(int cpu, u64 *min_perf)
>> +{
>> + return cppc_get_reg_val(cpu, MIN_PERF, min_perf);
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_get_min_perf);
>> +
>> +/**
>> + * cppc_set_min_perf - Write minimum performance register.
>> + * @cpu: CPU to which to write register.
>> + * @min_perf: the desired minimum performance value to be updated.
>> + */
>> +int cppc_set_min_perf(int cpu, u32 min_perf)
>> +{
>> + return cppc_set_reg_val(cpu, MIN_PERF, min_perf);
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_set_min_perf);
>> +
>> +/**
>> + * cppc_get_max_perf - Read maximum performance register.
>> + * @cpu: CPU from which to read register.
>> + * @max_perf: Return address.
>> + */
>> +int cppc_get_max_perf(int cpu, u64 *max_perf)
>> +{
>> + return cppc_get_reg_val(cpu, MAX_PERF, max_perf);
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_get_max_perf);
>> +
>> +/**
>> + * cppc_set_max_perf - Write maximum performance register.
>> + * @cpu: CPU to which to write register.
>> + * @max_perf: the desired maximum performance value to be updated.
>> + */
>> +int cppc_set_max_perf(int cpu, u32 max_perf)
>> +{
>> + return cppc_set_reg_val(cpu, MAX_PERF, max_perf);
>> +}
>> +EXPORT_SYMBOL_GPL(cppc_set_max_perf);
>> +
>> /**
>> * cppc_set_enable - Set to enable CPPC on the processor by writing
>> the
>> * Continuous Performance Control package EnableRegister field.
>> diff --git a/drivers/cpufreq/cppc_cpufreq.c
>> b/drivers/cpufreq/cppc_cpufreq.c
>> index 229880c4eedb..66e183b45fb0 100644
>> --- a/drivers/cpufreq/cppc_cpufreq.c
>> +++ b/drivers/cpufreq/cppc_cpufreq.c
>> @@ -28,6 +28,8 @@
>>
>> static struct cpufreq_driver cppc_cpufreq_driver;
>>
>> +static DEFINE_MUTEX(cppc_cpufreq_autonomous_lock);
>> +
>
> Shouldn't concurrent access be handled by the policy->rwsem ?
>
> I think this can be checked using either:
> - lockdep_assert_held_write(&policy->rwsem)
> - lockdep_assert_held_read(&policy->rwsem)
>
> in store/show_max_perf() for instance.
>
You're right. The cpufreq sysfs already holds policy->rwsem for
show/store callbacks. I'll remove the mutex and add lockdep
assertions for the expected locking.
--------
File: drivers/cpufreq/cpufreq.c
static ssize_t store(struct kobject *kobj, struct attribute *attr,
const char *buf, size_t count)
{
struct cpufreq_policy *policy = to_policy(kobj);
....
guard(cpufreq_policy_write)(policy);
--------
Thank you,
Sumit Gupta
>
>> #ifdef CONFIG_ACPI_CPPC_CPUFREQ_FIE
>> static enum {
>> FIE_UNSET = -1,
>> @@ -570,6 +572,35 @@ static void populate_efficiency_class(void)
>> }
>> #endif
>>
>> +/* Set min/max performance HW register and cache the value */
>> +static int cppc_cpufreq_set_mperf_reg(struct cpufreq_policy *policy,
>> + u64 val, bool is_min)
>> +{
>> + struct cppc_cpudata *cpu_data = policy->driver_data;
>> + struct cppc_perf_caps *caps = &cpu_data->perf_caps;
>> + unsigned int cpu = policy->cpu;
>> + u32 perf;
>> + int ret;
>> +
>> + perf = clamp(val, caps->lowest_perf, caps->highest_perf);
>> +
>> + ret = is_min ? cppc_set_min_perf(cpu, perf) :
>> + cppc_set_max_perf(cpu, perf);
>> + if (ret) {
>> + if (ret != -EOPNOTSUPP)
>> + pr_warn("CPU%d: set %s_perf=%u failed (%d)\n",
>> + cpu, is_min ? "min" : "max", perf, ret);
>> + return ret;
>> + }
>> +
>> + if (is_min)
>> + cpu_data->perf_ctrls.min_perf = perf;
>> + else
>> + cpu_data->perf_ctrls.max_perf = perf;
>> +
>> + return 0;
>> +}
>> +
>> static struct cppc_cpudata *cppc_cpufreq_get_cpu_data(unsigned int
>> cpu)
>> {
>> struct cppc_cpudata *cpu_data;
>> @@ -918,16 +949,142 @@ CPPC_CPUFREQ_ATTR_RW_U64(auto_act_window,
>> cppc_get_auto_act_window,
>> CPPC_CPUFREQ_ATTR_RW_U64(energy_performance_preference_val,
>> cppc_get_epp_perf, cppc_set_epp)
>>
>> +/**
>> + * show_min_perf - Show minimum performance as frequency (kHz)
>> + * @policy: cpufreq policy
>> + * @buf: buffer to write the frequency value to
>> + *
>> + * Reads the MIN_PERF register and converts the performance value to
>> + * frequency (kHz).
>> + */
>> +static ssize_t show_min_perf(struct cpufreq_policy *policy, char *buf)
>> +{
>> + struct cppc_cpudata *cpu_data = policy->driver_data;
>> + struct cppc_perf_caps *caps = &cpu_data->perf_caps;
>> + u64 perf;
>> + int ret;
>> +
>> + ret = cppc_get_min_perf(policy->cpu, &perf);
>> + if (ret == -EOPNOTSUPP)
>> + return sysfs_emit(buf, "<unsupported>\n");
>> + if (ret)
>> + return ret;
>> +
>> + /* Use lowest_perf if register is uninitialized (0) */
>> + if (perf == 0)
>> + perf = caps->lowest_perf;
>> +
>> + /* Convert performance to frequency (kHz) for user */
>> + return sysfs_emit(buf, "%u\n", cppc_perf_to_khz(caps, perf));
>> +}
>> +
>> +/**
>> + * store_min_perf - Set minimum performance from frequency (kHz)
>> + * @policy: cpufreq policy
>> + * @buf: buffer containing the frequency value
>> + * @count: size of @buf
>> + *
>> + * Converts the user-provided frequency (kHz) to a performance value
>> + * and writes it to the MIN_PERF register.
>> + */
>> +static ssize_t store_min_perf(struct cpufreq_policy *policy, const
>> char *buf,
>> + size_t count)
>> +{
>> + struct cppc_cpudata *cpu_data = policy->driver_data;
>> + unsigned int freq_khz;
>> + u64 perf;
>> + int ret;
>> +
>> + ret = kstrtouint(buf, 0, &freq_khz);
>> + if (ret)
>> + return ret;
>> +
>> + /* Convert frequency (kHz) to performance value */
>> + perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
>> +
>> + guard(mutex)(&cppc_cpufreq_autonomous_lock);
>> + ret = cppc_cpufreq_set_mperf_reg(policy, perf, true);
>> + if (ret)
>> + return ret;
>> +
>> + return count;
>> +}
>> +
>> +/**
>> + * show_max_perf - Show maximum performance as frequency (kHz)
>> + * @policy: cpufreq policy
>> + * @buf: buffer to write the frequency value to
>> + *
>> + * Reads the MAX_PERF register and converts the performance value to
>> + * frequency (kHz).
>> + */
>> +static ssize_t show_max_perf(struct cpufreq_policy *policy, char *buf)
>> +{
>> + struct cppc_cpudata *cpu_data = policy->driver_data;
>> + struct cppc_perf_caps *caps = &cpu_data->perf_caps;
>> + u64 perf;
>> + int ret;
>> +
>> + ret = cppc_get_max_perf(policy->cpu, &perf);
>> + if (ret == -EOPNOTSUPP)
>> + return sysfs_emit(buf, "<unsupported>\n");
>> + if (ret)
>> + return ret;
>> +
>> + /* Use highest_perf if register is uninitialized or out of
>> range */
>> + if (perf == 0 || perf > caps->highest_perf)
>> + perf = caps->highest_perf;
>> +
>> + /* Convert performance to frequency (kHz) for user */
>> + return sysfs_emit(buf, "%u\n", cppc_perf_to_khz(caps, perf));
>> +}
>> +
>> +/**
>> + * store_max_perf - Set maximum performance from frequency (kHz)
>> + * @policy: cpufreq policy
>> + * @buf: buffer containing the frequency value
>> + * @count: size of @buf
>> + *
>> + * Converts the user-provided frequency (kHz) to a performance value
>> + * and writes it to the MAX_PERF register.
>> + */
>> +static ssize_t store_max_perf(struct cpufreq_policy *policy, const
>> char *buf,
>> + size_t count)
>> +{
>> + struct cppc_cpudata *cpu_data = policy->driver_data;
>> + unsigned int freq_khz;
>> + u64 perf;
>> + int ret;
>> +
>> + ret = kstrtouint(buf, 0, &freq_khz);
>> + if (ret)
>> + return ret;
>> +
>> + /* Convert frequency (kHz) to performance value */
>> + perf = cppc_khz_to_perf(&cpu_data->perf_caps, freq_khz);
>> +
>> + guard(mutex)(&cppc_cpufreq_autonomous_lock);
>> + ret = cppc_cpufreq_set_mperf_reg(policy, perf, false);
>> + if (ret)
>> + return ret;
>> +
>> + return count;
>> +}
>> +
>> cpufreq_freq_attr_ro(freqdomain_cpus);
>> cpufreq_freq_attr_rw(auto_select);
>> cpufreq_freq_attr_rw(auto_act_window);
>> cpufreq_freq_attr_rw(energy_performance_preference_val);
>> +cpufreq_freq_attr_rw(min_perf);
>> +cpufreq_freq_attr_rw(max_perf);
>>
>> static struct freq_attr *cppc_cpufreq_attr[] = {
>> &freqdomain_cpus,
>> &auto_select,
>> &auto_act_window,
>> &energy_performance_preference_val,
>> + &min_perf,
>> + &max_perf,
>> NULL,
>> };
>>
>> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
>> index 3fc796c0d902..b358440cd0e2 100644
>> --- a/include/acpi/cppc_acpi.h
>> +++ b/include/acpi/cppc_acpi.h
>> @@ -174,6 +174,10 @@ extern int cppc_get_auto_act_window(int cpu, u64
>> *auto_act_window);
>> extern int cppc_set_auto_act_window(int cpu, u64 auto_act_window);
>> extern int cppc_get_auto_sel(int cpu, bool *enable);
>> extern int cppc_set_auto_sel(int cpu, bool enable);
>> +extern int cppc_get_min_perf(int cpu, u64 *min_perf);
>> +extern int cppc_set_min_perf(int cpu, u32 min_perf);
>> +extern int cppc_get_max_perf(int cpu, u64 *max_perf);
>> +extern int cppc_set_max_perf(int cpu, u32 max_perf);
>> extern int amd_get_highest_perf(unsigned int cpu, u32 *highest_perf);
>> extern int amd_get_boost_ratio_numerator(unsigned int cpu, u64
>> *numerator);
>> extern int amd_detect_prefcore(bool *detected);
>> @@ -270,6 +274,22 @@ static inline int cppc_set_auto_sel(int cpu,
>> bool enable)
>> {
>> return -EOPNOTSUPP;
>> }
>> +static inline int cppc_get_min_perf(int cpu, u64 *min_perf)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +static inline int cppc_set_min_perf(int cpu, u32 min_perf)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +static inline int cppc_get_max_perf(int cpu, u64 *max_perf)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +static inline int cppc_set_max_perf(int cpu, u32 max_perf)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> static inline int amd_get_highest_perf(unsigned int cpu, u32
>> *highest_perf)
>> {
>> return -ENODEV;
Powered by blists - more mailing lists