[PATCH v8 0/2] cpufreq: Introduce boost frequency QoS

[PATCH v8 0/2] cpufreq: Introduce boost frequency QoS

[Pierre Gondois]

The Power Management Quality of Service (PM QoS) allows to
aggregate constraints from multiple entities. It is currently
used to manage the min/max frequency of a given policy.

Frequency constraints can come from:
- Thermal framework: acpi_thermal_cpufreq_init()
- Firmware: _PPC objects: acpi_processor_ppc_init()
- User: by setting policyX/scaling_[min|max]_freq
The minimum of the max frequency constraints is used to compute
the resulting maximum allowed frequency.

When enabling boost frequencies, the same frequency request object
(policy->max_freq_req) as to handle requests from users is used.
As a result, when setting:
- scaling_max_freq
- boost
The last sysfs file used overwrites the request from the other
sysfs file.

To avoid this:
1. Create a per-policy boost_freq_req to save the boost
constraints instead of overwriting the last scaling_max_freq
constraint.

2. policy_set_boost() calls the cpufreq set_boost callback.
Update the newly added boost_freq_req request from there:
- whenever boost is toggled
- to cover all possible paths

3. In the existing set_boost() callbacks:
- Don't update policy->max as this is done through the qos notifier
  cpufreq_notifier_max() which calls cpufreq_set_policy().
- Remove freq_qos_update_request() calls as the qos request is now
  done in policy_set_boost() and updates the new boost_freq_req

---

E.g.:
On a Juno with available frequencies: 600.000, 1.000.000
Boost frequencies: 1.200.000
Using the cppc-cpufreq driver.

---
Without the patches:
# ## Init state
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

# echo 700000 > scaling_max_freq
scaling_max_freq:700000
cpuinfo_max_freq:1000000

# echo 1 > ../boost
scaling_max_freq:1200000
cpuinfo_max_freq:1200000

# echo 800000 > scaling_max_freq
scaling_max_freq:800000
cpuinfo_max_freq:1200000

# echo 0 > ../boost
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

---
With the patches:
# ## Init
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

# echo 700000 > scaling_max_freq
scaling_max_freq:700000
cpuinfo_max_freq:1000000

# echo 1 > ../boost
scaling_max_freq:700000
cpuinfo_max_freq:1200000

# echo 800000 > scaling_max_freq
scaling_max_freq:800000
cpuinfo_max_freq:1200000

# echo 0 > ../boost
scaling_max_freq:800000
cpuinfo_max_freq:1000000

With the patches, the maximum scaling frequency requested is
conserved even though boosting is enabled/disabled.

---

Note:
It seems that there is a confusion in the cpufreq framework between:
- the min/max frequency requested by the user
- the min/max frequency constraint applied when selecting a frequency.

E.g:
A.
$ echo XXX > scaling_max_freq
updates the max_freq_req QoS request.

B.
$ cat scaling_max_freq
shows the content of policy->max, which is the not representing
the value of the max_freq_req QoS request.

C.
Whenever policy->max is accessed in the cpufreq framework,
the aggregation of all the requests on the maximum frequency should
be used instead.

cpufreq_set_policy() aggregates min/max constraints and
writes the resulting value in policy->min/max. These values
are then used in the cpufreq drivers.

Creating a clear distinction would be doable but quite invasive.
This patchset focuses on handling the boost frequency QoS request
first and should not change the current behaviour of policy->min
and max.

---

v1: https://lore.kernel.org/all/20251204101344.192678-1-pierre.gondois@arm.com/#t
v2: https://lore.kernel.org/all/20251208105933.1369125-1-pierre.gondois@arm.com/#t
Changes:
- Fixed error path
- Integrated [PATCH 1/4] Revert "cpufreq: Fix re-boost issue after hotplugging a CPU"
  to another patch
v3:
Changes:
- Fixed error path
- Extracted the revert of:
  "cpufreq: Fix re-boost issue after hotplugging a CPU"
  for clarity purpose
- Set cpuinfo.max_freq as a max_freq_req QoS constraint by default
New patches:
- "cpufreq: Allow decreasing cpuinfo.max_freq"
- "cpufreq: Set policy->min and max as QoS constraints"
v4:
- Correct reported issues
v5:
- Corrections
v6:
- Folded patches:
  - cpufreq: Centralize boost freq QoS requests
  - cpufreq: Update .set_boost() callbacks to rely on boost_freq_req
  inside:
  - cpufreq: Add boost_freq_req QoS request
- Simplified allocation handling of boost_freq_req
- Removed unnecessary bits
v7:
- Removed the following patches to submit them separately
  - cpufreq: Set policy->min and max as real QoS constraints
  - cpufreq/freq_table: Allow decreasing cpuinfo.max_freq
- Fixed blocking_notifier_call_chain() call order when removing
  a policy.
- Updated the commit message of:
  - cpufreq: Remove per-CPU QoS constraint
v8:
- Renamed first patch
- Small corrections to second patch.

Pierre Gondois (2):
  cpufreq: Remove max_freq_req update for pre-existing policy
  cpufreq: Add boost_freq_req QoS request

 drivers/cpufreq/amd-pstate.c   |  2 --
 drivers/cpufreq/cppc_cpufreq.c | 10 ++-----
 drivers/cpufreq/cpufreq.c      | 50 +++++++++++++++++++++-------------
 include/linux/cpufreq.h        |  1 +
 4 files changed, 34 insertions(+), 29 deletions(-)

--
2.43.0

[PATCH v8 1/2] cpufreq: Remove max_freq_req update for pre-existing policy

[Pierre Gondois]

policy->max_freq_req QoS constraint represents the maximal allowed
frequency than can be requested. It is set by:
- writing to policyX/scaling_max sysfs file
- toggling the cpufreq/boost sysfs file

Upon calling freq_qos_update_request(), a successful update
of the max_freq_req value triggers cpufreq_notifier_max(),
followed by cpufreq_set_policy() which update the requested
frequency for the policy.
If the new max_freq_req value is not different from the
original value, no frequency update is triggered.

In a specific sequence of toggling:
- cpufreq/boost sysfs file
- CPU hot-plugging
a CPU could end up with boost enabled but running at the
maximal non-boost frequency, cpufreq_notifier_max() not being
triggered. The following fixed that:
commit 1608f0230510 ("cpufreq: Fix re-boost issue after hotplugging
a CPU")

The following:
commit dd016f379ebc ("cpufreq: Introduce a more generic way to
set default per-policy boost flag")
also fixed the issue by correctly setting the max_freq_req
constraint of a policy that is re-activated. This makes the
first fix unnecessary.

As the original issue is fixed by another method,
this patch reverts:
commit 1608f0230510 ("cpufreq: Fix re-boost issue after hotplugging
a CPU")

Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
---
 drivers/cpufreq/cpufreq.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 277884d91913c..5757f12633d16 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1487,10 +1487,6 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
 
 		blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
 				CPUFREQ_CREATE_POLICY, policy);
-	} else {
-		ret = freq_qos_update_request(policy->max_freq_req, policy->max);
-		if (ret < 0)
-			goto out_destroy_policy;
 	}
 
 	if (cpufreq_driver->get && has_target()) {
-- 
2.43.0

[PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Pierre Gondois]

The Power Management Quality of Service (PM QoS) allows to
aggregate constraints from multiple entities. It is currently
used to manage the min/max frequency of a given policy.

Frequency constraints can come for instance from:
- Thermal framework: acpi_thermal_cpufreq_init()
- Firmware: _PPC objects: acpi_processor_ppc_init()
- User: by setting policyX/scaling_[min|max]_freq
The minimum of the max frequency constraints is used to compute
the resulting maximum allowed frequency.

When enabling boost frequencies, the same frequency request object
(policy->max_freq_req) as to handle requests from users is used.
As a result, when setting:
- scaling_max_freq
- boost
The last sysfs file used overwrites the request from the other
sysfs file.

To avoid this, create a per-policy boost_freq_req to save the boost
constraints instead of overwriting the last scaling_max_freq
constraint.

policy_set_boost() calls the cpufreq set_boost callback.
Update the newly added boost_freq_req request from there:
- whenever boost is toggled
- to cover all possible paths

In the existing .set_boost() callbacks:
- Don't update policy->max as this is done through the qos notifier
  cpufreq_notifier_max() which calls cpufreq_set_policy().
- Remove freq_qos_update_request() calls as the qos request is now
  done in policy_set_boost() and updates the new boost_freq_req

$ ## Init state
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

$ echo 700000 > scaling_max_freq
scaling_max_freq:700000
cpuinfo_max_freq:1000000

$ echo 1 > ../boost
scaling_max_freq:1200000
cpuinfo_max_freq:1200000

$ echo 800000 > scaling_max_freq
scaling_max_freq:800000
cpuinfo_max_freq:1200000

$ ## Final step:
$ ## Without the patches:
$ echo 0 > ../boost
scaling_max_freq:1000000
cpuinfo_max_freq:1000000

$ ## With the patches:
$ echo 0 > ../boost
scaling_max_freq:800000
cpuinfo_max_freq:1000000

Note:
cpufreq_frequency_table_cpuinfo() updates policy->min
and max from:
A.
cpufreq_boost_set_sw()
\-cpufreq_frequency_table_cpuinfo()
B.
cpufreq_policy_online()
\-cpufreq_table_validate_and_sort()
  \-cpufreq_frequency_table_cpuinfo()
Keep these updates as some drivers expect policy->min and
max to be set through B.

Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
---
 drivers/cpufreq/amd-pstate.c   |  2 --
 drivers/cpufreq/cppc_cpufreq.c | 10 ++------
 drivers/cpufreq/cpufreq.c      | 46 +++++++++++++++++++++++-----------
 include/linux/cpufreq.h        |  1 +
 4 files changed, 34 insertions(+), 25 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 5aa9fcd80cf51..d0675d6a19fe1 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -769,8 +769,6 @@ static int amd_pstate_cpu_boost_update(struct cpufreq_policy *policy, bool on)
 	else if (policy->cpuinfo.max_freq > nominal_freq)
 		policy->cpuinfo.max_freq = nominal_freq;
 
-	policy->max = policy->cpuinfo.max_freq;
-
 	if (cppc_state == AMD_PSTATE_PASSIVE) {
 		ret = freq_qos_update_request(&cpudata->req[1], policy->cpuinfo.max_freq);
 		if (ret < 0)
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index 011f35cb47b94..f4f574fbe547b 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -807,17 +807,11 @@ static int cppc_cpufreq_set_boost(struct cpufreq_policy *policy, int state)
 {
 	struct cppc_cpudata *cpu_data = policy->driver_data;
 	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
-	int ret;
 
 	if (state)
-		policy->max = cppc_perf_to_khz(caps, caps->highest_perf);
+		policy->cpuinfo.max_freq = cppc_perf_to_khz(caps, caps->highest_perf);
 	else
-		policy->max = cppc_perf_to_khz(caps, caps->nominal_perf);
-	policy->cpuinfo.max_freq = policy->max;
-
-	ret = freq_qos_update_request(policy->max_freq_req, policy->max);
-	if (ret < 0)
-		return ret;
+		policy->cpuinfo.max_freq = cppc_perf_to_khz(caps, caps->nominal_perf);
 
 	return 0;
 }
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 5757f12633d16..d2f393d738a39 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -609,10 +609,19 @@ static int policy_set_boost(struct cpufreq_policy *policy, bool enable)
 	policy->boost_enabled = enable;
 
 	ret = cpufreq_driver->set_boost(policy, enable);
-	if (ret)
+	if (ret) {
 		policy->boost_enabled = !policy->boost_enabled;
+		return ret;
+	}
 
-	return ret;
+	ret = freq_qos_update_request(policy->boost_freq_req, policy->cpuinfo.max_freq);
+	if (ret < 0) {
+		policy->boost_enabled = !policy->boost_enabled;
+		cpufreq_driver->set_boost(policy, policy->boost_enabled);
+		return ret;
+	}
+
+	return 0;
 }
 
 static ssize_t store_local_boost(struct cpufreq_policy *policy,
@@ -1377,6 +1386,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
 	}
 
 	freq_qos_remove_request(policy->min_freq_req);
+	freq_qos_remove_request(policy->boost_freq_req);
 	kfree(policy->min_freq_req);
 
 	cpufreq_policy_put_kobj(policy);
@@ -1445,26 +1455,38 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
 	cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
 
 	if (new_policy) {
+		unsigned int count;
+
 		for_each_cpu(j, policy->related_cpus) {
 			per_cpu(cpufreq_cpu_data, j) = policy;
 			add_cpu_dev_symlink(policy, j, get_cpu_device(j));
 		}
 
-		policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req),
+		count = policy->boost_supported ? 3 : 2;
+		policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
 					       GFP_KERNEL);
 		if (!policy->min_freq_req) {
 			ret = -ENOMEM;
 			goto out_destroy_policy;
 		}
 
+		if (policy->boost_supported) {
+			policy->boost_freq_req = policy->min_freq_req + 2;
+
+			ret = freq_qos_add_request(&policy->constraints,
+						   policy->boost_freq_req,
+						   FREQ_QOS_MAX,
+						   policy->cpuinfo.max_freq);
+			if (ret < 0) {
+				policy->boost_freq_req = NULL;
+				goto out_destroy_policy;
+			}
+		}
+
 		ret = freq_qos_add_request(&policy->constraints,
 					   policy->min_freq_req, FREQ_QOS_MIN,
 					   FREQ_QOS_MIN_DEFAULT_VALUE);
 		if (ret < 0) {
-			/*
-			 * So we don't call freq_qos_remove_request() for an
-			 * uninitialized request.
-			 */
 			kfree(policy->min_freq_req);
 			policy->min_freq_req = NULL;
 			goto out_destroy_policy;
@@ -2788,16 +2810,10 @@ int cpufreq_boost_set_sw(struct cpufreq_policy *policy, int state)
 		return -ENXIO;
 
 	ret = cpufreq_frequency_table_cpuinfo(policy);
-	if (ret) {
+	if (ret)
 		pr_err("%s: Policy frequency update failed\n", __func__);
-		return ret;
-	}
-
-	ret = freq_qos_update_request(policy->max_freq_req, policy->max);
-	if (ret < 0)
-		return ret;
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(cpufreq_boost_set_sw);
 
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index cc894fc389710..89157e367eefa 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -81,6 +81,7 @@ struct cpufreq_policy {
 	struct freq_constraints	constraints;
 	struct freq_qos_request	*min_freq_req;
 	struct freq_qos_request	*max_freq_req;
+	struct freq_qos_request *boost_freq_req;
 
 	struct cpufreq_frequency_table	*freq_table;
 	enum cpufreq_table_sorting freq_table_sorted;
-- 
2.43.0

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Zhongqiu Han]

On 3/27/2026 4:44 AM, Pierre Gondois wrote:
> The Power Management Quality of Service (PM QoS) allows to
> aggregate constraints from multiple entities. It is currently
> used to manage the min/max frequency of a given policy.
> 
> Frequency constraints can come for instance from:
> - Thermal framework: acpi_thermal_cpufreq_init()
> - Firmware: _PPC objects: acpi_processor_ppc_init()
> - User: by setting policyX/scaling_[min|max]_freq
> The minimum of the max frequency constraints is used to compute
> the resulting maximum allowed frequency.
> 
> When enabling boost frequencies, the same frequency request object
> (policy->max_freq_req) as to handle requests from users is used.
> As a result, when setting:
> - scaling_max_freq
> - boost
> The last sysfs file used overwrites the request from the other
> sysfs file.
> 
> To avoid this, create a per-policy boost_freq_req to save the boost
> constraints instead of overwriting the last scaling_max_freq
> constraint.
> 
> policy_set_boost() calls the cpufreq set_boost callback.
> Update the newly added boost_freq_req request from there:
> - whenever boost is toggled
> - to cover all possible paths
> 
> In the existing .set_boost() callbacks:
> - Don't update policy->max as this is done through the qos notifier
>    cpufreq_notifier_max() which calls cpufreq_set_policy().
> - Remove freq_qos_update_request() calls as the qos request is now
>    done in policy_set_boost() and updates the new boost_freq_req
> 
> $ ## Init state
> scaling_max_freq:1000000
> cpuinfo_max_freq:1000000
> 
> $ echo 700000 > scaling_max_freq
> scaling_max_freq:700000
> cpuinfo_max_freq:1000000
> 
> $ echo 1 > ../boost
> scaling_max_freq:1200000
> cpuinfo_max_freq:1200000
> 
> $ echo 800000 > scaling_max_freq
> scaling_max_freq:800000
> cpuinfo_max_freq:1200000
> 
> $ ## Final step:
> $ ## Without the patches:
> $ echo 0 > ../boost
> scaling_max_freq:1000000
> cpuinfo_max_freq:1000000
> 
> $ ## With the patches:
> $ echo 0 > ../boost
> scaling_max_freq:800000
> cpuinfo_max_freq:1000000
> 
> Note:
> cpufreq_frequency_table_cpuinfo() updates policy->min
> and max from:
> A.
> cpufreq_boost_set_sw()
> \-cpufreq_frequency_table_cpuinfo()
> B.
> cpufreq_policy_online()
> \-cpufreq_table_validate_and_sort()
>    \-cpufreq_frequency_table_cpuinfo()
> Keep these updates as some drivers expect policy->min and
> max to be set through B.
> 
> Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
> Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
> ---
>   drivers/cpufreq/amd-pstate.c   |  2 --
>   drivers/cpufreq/cppc_cpufreq.c | 10 ++------
>   drivers/cpufreq/cpufreq.c      | 46 +++++++++++++++++++++++-----------
>   include/linux/cpufreq.h        |  1 +
>   4 files changed, 34 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 5aa9fcd80cf51..d0675d6a19fe1 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -769,8 +769,6 @@ static int amd_pstate_cpu_boost_update(struct cpufreq_policy *policy, bool on)
>   	else if (policy->cpuinfo.max_freq > nominal_freq)
>   		policy->cpuinfo.max_freq = nominal_freq;
>   
> -	policy->max = policy->cpuinfo.max_freq;
> -
>   	if (cppc_state == AMD_PSTATE_PASSIVE) {
>   		ret = freq_qos_update_request(&cpudata->req[1], policy->cpuinfo.max_freq);
>   		if (ret < 0)
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 011f35cb47b94..f4f574fbe547b 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -807,17 +807,11 @@ static int cppc_cpufreq_set_boost(struct cpufreq_policy *policy, int state)
>   {
>   	struct cppc_cpudata *cpu_data = policy->driver_data;
>   	struct cppc_perf_caps *caps = &cpu_data->perf_caps;
> -	int ret;
>   
>   	if (state)
> -		policy->max = cppc_perf_to_khz(caps, caps->highest_perf);
> +		policy->cpuinfo.max_freq = cppc_perf_to_khz(caps, caps->highest_perf);
>   	else
> -		policy->max = cppc_perf_to_khz(caps, caps->nominal_perf);
> -	policy->cpuinfo.max_freq = policy->max;
> -
> -	ret = freq_qos_update_request(policy->max_freq_req, policy->max);
> -	if (ret < 0)
> -		return ret;
> +		policy->cpuinfo.max_freq = cppc_perf_to_khz(caps, caps->nominal_perf);
>   
>   	return 0;
>   }
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 5757f12633d16..d2f393d738a39 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -609,10 +609,19 @@ static int policy_set_boost(struct cpufreq_policy *policy, bool enable)
>   	policy->boost_enabled = enable;
>   
>   	ret = cpufreq_driver->set_boost(policy, enable);
> -	if (ret)
> +	if (ret) {
>   		policy->boost_enabled = !policy->boost_enabled;
> +		return ret;
> +	}
>   
> -	return ret;
> +	ret = freq_qos_update_request(policy->boost_freq_req, policy->cpuinfo.max_freq);
> +	if (ret < 0) {
> +		policy->boost_enabled = !policy->boost_enabled;
> +		cpufreq_driver->set_boost(policy, policy->boost_enabled);
> +		return ret;
> +	}
> +
> +	return 0;
>   }
>   
>   static ssize_t store_local_boost(struct cpufreq_policy *policy,
> @@ -1377,6 +1386,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>   	}
>   
>   	freq_qos_remove_request(policy->min_freq_req);
> +	freq_qos_remove_request(policy->boost_freq_req);
>   	kfree(policy->min_freq_req);
>   
>   	cpufreq_policy_put_kobj(policy);
> @@ -1445,26 +1455,38 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
>   	cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
>   
>   	if (new_policy) {
> +		unsigned int count;
> +
>   		for_each_cpu(j, policy->related_cpus) {
>   			per_cpu(cpufreq_cpu_data, j) = policy;
>   			add_cpu_dev_symlink(policy, j, get_cpu_device(j));
>   		}
>   
> -		policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req),
> +		count = policy->boost_supported ? 3 : 2;
> +		policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
>   					       GFP_KERNEL);
>   		if (!policy->min_freq_req) {
>   			ret = -ENOMEM;
>   			goto out_destroy_policy;
>   		}
>   
> +		if (policy->boost_supported) {
> +			policy->boost_freq_req = policy->min_freq_req + 2;
> +
> +			ret = freq_qos_add_request(&policy->constraints,
> +						   policy->boost_freq_req,
> +						   FREQ_QOS_MAX,
> +						   policy->cpuinfo.max_freq);
> +			if (ret < 0) {
> +				policy->boost_freq_req = NULL;
> +				goto out_destroy_policy;
> +			}
> +		}
> +
>   		ret = freq_qos_add_request(&policy->constraints,
>   					   policy->min_freq_req, FREQ_QOS_MIN,
>   					   FREQ_QOS_MIN_DEFAULT_VALUE);
>   		if (ret < 0) {
> -			/*
> -			 * So we don't call freq_qos_remove_request() for an
> -			 * uninitialized request.
> -			 */
>   			kfree(policy->min_freq_req);
>   			policy->min_freq_req = NULL;
>   			goto out_destroy_policy;

Hi Pierre, Viresh,

Sorry for the late follow-up on v8. While re-reading the patch, I
noticed a potential UAF issue on an error path — I might be missing
something, so I'd appreciate a double-check.

min_freq_req, max_freq_req and boost_freq_req all point into the same
contiguous kzalloc'd block:

slot0 (min_freq_req + 0) -> min_freq_req
slot1 (min_freq_req + 1) -> max_freq_req
slot2 (min_freq_req + 2) -> boost_freq_req

If boost_freq_req is successfully added to the QoS constraints list, but
the subsequent freq_qos_add_request() for min_freq_req fails, the error
path does:

kfree(policy->min_freq_req); /* frees the entire block, including slot2
*/
policy->min_freq_req = NULL;
goto out_destroy_policy;

policy->boost_freq_req is not set to NULL here, so it becomes a dangling
pointer into freed memory.
cpufreq_policy_free() is then called from cpufreq_online() and does:

freq_qos_remove_request(policy->boost_freq_req); /* UAF */
or this boost qos req will leak.


If freq_qos_add_request() for min_freq_req fails, maybe we can remove
boost qos first, such as:

if (ret < 0) {
	if (policy->boost_freq_req) {
		freq_qos_remove_request(policy->boost_freq_req);
		policy->boost_freq_req = NULL;
	}
	kfree(policy->min_freq_req);
	policy->min_freq_req = NULL;
	goto out_destroy_policy;
}



Besides, if freq_qos_add_request() for boost_freq_req fails first on
cpufreq_policy_online(),  policy->min_freq_req is valid pointer but qos
req is inactive, will trigger one warn on
freq_qos_remove_request(policy->min_freq_req) {
	if (WARN(!freq_qos_request_active(req),
		"%s() called for unknown object\n", __func__))
		return -EINVAL;
}


> @@ -2788,16 +2810,10 @@ int cpufreq_boost_set_sw(struct cpufreq_policy *policy, int state)
>   		return -ENXIO;
>   
>   	ret = cpufreq_frequency_table_cpuinfo(policy);
> -	if (ret) {
> +	if (ret)
>   		pr_err("%s: Policy frequency update failed\n", __func__);
> -		return ret;
> -	}
> -
> -	ret = freq_qos_update_request(policy->max_freq_req, policy->max);
> -	if (ret < 0)
> -		return ret;
>   
> -	return 0;
> +	return ret;
>   }
>   EXPORT_SYMBOL_GPL(cpufreq_boost_set_sw);
>   
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index cc894fc389710..89157e367eefa 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -81,6 +81,7 @@ struct cpufreq_policy {
>   	struct freq_constraints	constraints;
>   	struct freq_qos_request	*min_freq_req;
>   	struct freq_qos_request	*max_freq_req;
> +	struct freq_qos_request *boost_freq_req;
>   
>   	struct cpufreq_frequency_table	*freq_table;
>   	enum cpufreq_table_sorting freq_table_sorted;


-- 
Thx and BRs,
Zhongqiu Han

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[zhenglifeng (A)]

On 3/29/2026 5:00 PM, Zhongqiu Han wrote:
>> @@ -1377,6 +1386,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>>       }
>>         freq_qos_remove_request(policy->min_freq_req);
>> +    freq_qos_remove_request(policy->boost_freq_req);
>>       kfree(policy->min_freq_req);
>>         cpufreq_policy_put_kobj(policy);
>> @@ -1445,26 +1455,38 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
>>       cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
>>         if (new_policy) {
>> +        unsigned int count;
>> +
>>           for_each_cpu(j, policy->related_cpus) {
>>               per_cpu(cpufreq_cpu_data, j) = policy;
>>               add_cpu_dev_symlink(policy, j, get_cpu_device(j));
>>           }
>>   -        policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req),
>> +        count = policy->boost_supported ? 3 : 2;
>> +        policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
>>                              GFP_KERNEL);
>>           if (!policy->min_freq_req) {
>>               ret = -ENOMEM;
>>               goto out_destroy_policy;
>>           }
>>   +        if (policy->boost_supported) {
>> +            policy->boost_freq_req = policy->min_freq_req + 2;
>> +
>> +            ret = freq_qos_add_request(&policy->constraints,
>> +                           policy->boost_freq_req,
>> +                           FREQ_QOS_MAX,
>> +                           policy->cpuinfo.max_freq);
>> +            if (ret < 0) {
>> +                policy->boost_freq_req = NULL;
>> +                goto out_destroy_policy;
>> +            }
>> +        }
>> +
>>           ret = freq_qos_add_request(&policy->constraints,
>>                          policy->min_freq_req, FREQ_QOS_MIN,
>>                          FREQ_QOS_MIN_DEFAULT_VALUE);
>>           if (ret < 0) {
>> -            /*
>> -             * So we don't call freq_qos_remove_request() for an
>> -             * uninitialized request.
>> -             */
>>               kfree(policy->min_freq_req);
>>               policy->min_freq_req = NULL;
>>               goto out_destroy_policy;
> 
> Hi Pierre, Viresh,
> 
> Sorry for the late follow-up on v8. While re-reading the patch, I
> noticed a potential UAF issue on an error path — I might be missing
> something, so I'd appreciate a double-check.
> 
> min_freq_req, max_freq_req and boost_freq_req all point into the same
> contiguous kzalloc'd block:
> 
> slot0 (min_freq_req + 0) -> min_freq_req
> slot1 (min_freq_req + 1) -> max_freq_req
> slot2 (min_freq_req + 2) -> boost_freq_req
> 
> If boost_freq_req is successfully added to the QoS constraints list, but
> the subsequent freq_qos_add_request() for min_freq_req fails, the error
> path does:
> 
> kfree(policy->min_freq_req); /* frees the entire block, including slot2
> */
> policy->min_freq_req = NULL;
> goto out_destroy_policy;
> 
> policy->boost_freq_req is not set to NULL here, so it becomes a dangling
> pointer into freed memory.
> cpufreq_policy_free() is then called from cpufreq_online() and does:
> 
> freq_qos_remove_request(policy->boost_freq_req); /* UAF */
> or this boost qos req will leak.
> 

Good catch!

How about remove the kfree() here and just leave it to
cpufreq_policy_free()?

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Zhongqiu Han]

On 3/30/2026 10:10 AM, zhenglifeng (A) wrote:
> On 3/29/2026 5:00 PM, Zhongqiu Han wrote:
>>> @@ -1377,6 +1386,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>>>        }
>>>          freq_qos_remove_request(policy->min_freq_req);
>>> +    freq_qos_remove_request(policy->boost_freq_req);
>>>        kfree(policy->min_freq_req);
>>>          cpufreq_policy_put_kobj(policy);
>>> @@ -1445,26 +1455,38 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
>>>        cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
>>>          if (new_policy) {
>>> +        unsigned int count;
>>> +
>>>            for_each_cpu(j, policy->related_cpus) {
>>>                per_cpu(cpufreq_cpu_data, j) = policy;
>>>                add_cpu_dev_symlink(policy, j, get_cpu_device(j));
>>>            }
>>>    -        policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req),
>>> +        count = policy->boost_supported ? 3 : 2;
>>> +        policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
>>>                               GFP_KERNEL);
>>>            if (!policy->min_freq_req) {
>>>                ret = -ENOMEM;
>>>                goto out_destroy_policy;
>>>            }
>>>    +        if (policy->boost_supported) {
>>> +            policy->boost_freq_req = policy->min_freq_req + 2;
>>> +
>>> +            ret = freq_qos_add_request(&policy->constraints,
>>> +                           policy->boost_freq_req,
>>> +                           FREQ_QOS_MAX,
>>> +                           policy->cpuinfo.max_freq);
>>> +            if (ret < 0) {
>>> +                policy->boost_freq_req = NULL;
>>> +                goto out_destroy_policy;
>>> +            }
>>> +        }
>>> +
>>>            ret = freq_qos_add_request(&policy->constraints,
>>>                           policy->min_freq_req, FREQ_QOS_MIN,
>>>                           FREQ_QOS_MIN_DEFAULT_VALUE);
>>>            if (ret < 0) {
>>> -            /*
>>> -             * So we don't call freq_qos_remove_request() for an
>>> -             * uninitialized request.
>>> -             */
>>>                kfree(policy->min_freq_req);
>>>                policy->min_freq_req = NULL;
>>>                goto out_destroy_policy;
>>
>> Hi Pierre, Viresh,
>>
>> Sorry for the late follow-up on v8. While re-reading the patch, I
>> noticed a potential UAF issue on an error path — I might be missing
>> something, so I'd appreciate a double-check.
>>
>> min_freq_req, max_freq_req and boost_freq_req all point into the same
>> contiguous kzalloc'd block:
>>
>> slot0 (min_freq_req + 0) -> min_freq_req
>> slot1 (min_freq_req + 1) -> max_freq_req
>> slot2 (min_freq_req + 2) -> boost_freq_req
>>
>> If boost_freq_req is successfully added to the QoS constraints list, but
>> the subsequent freq_qos_add_request() for min_freq_req fails, the error
>> path does:
>>
>> kfree(policy->min_freq_req); /* frees the entire block, including slot2
>> */
>> policy->min_freq_req = NULL;
>> goto out_destroy_policy;
>>
>> policy->boost_freq_req is not set to NULL here, so it becomes a dangling
>> pointer into freed memory.
>> cpufreq_policy_free() is then called from cpufreq_online() and does:
>>
>> freq_qos_remove_request(policy->boost_freq_req); /* UAF */
>> or this boost qos req will leak.
>>
> 
> Good catch!
> 
> How about remove the kfree() here and just leave it to
> cpufreq_policy_free()?
> 

Thanks for the suggestion — this is another fix approach we can
explore, but there seems to be a small caveat.

Some additional changes would still be needed; otherwise, removing the
kfree() here and deferring it to cpufreq_policy_free() can lead to a
warning.

The reason is that we neither free policy->min_freq_req nor set policy
->min_freq_req = NULL. As a result, when cpufreq_policy_free() later
calls freq_qos_remove_request(policy->min_freq_req), it hits the
following warning:

if (WARN(!freq_qos_request_active(req),
	"%s() called for unknown object\n", __func__))
	return -EINVAL;




-- 
Thx and BRs,
Zhongqiu Han

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[zhenglifeng (A)]

On 3/30/2026 12:00 PM, Zhongqiu Han wrote:
> On 3/30/2026 10:10 AM, zhenglifeng (A) wrote:
>> On 3/29/2026 5:00 PM, Zhongqiu Han wrote:
>>>> @@ -1377,6 +1386,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>>>>        }
>>>>          freq_qos_remove_request(policy->min_freq_req);
>>>> +    freq_qos_remove_request(policy->boost_freq_req);
>>>>        kfree(policy->min_freq_req);
>>>>          cpufreq_policy_put_kobj(policy);
>>>> @@ -1445,26 +1455,38 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
>>>>        cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
>>>>          if (new_policy) {
>>>> +        unsigned int count;
>>>> +
>>>>            for_each_cpu(j, policy->related_cpus) {
>>>>                per_cpu(cpufreq_cpu_data, j) = policy;
>>>>                add_cpu_dev_symlink(policy, j, get_cpu_device(j));
>>>>            }
>>>>    -        policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req),
>>>> +        count = policy->boost_supported ? 3 : 2;
>>>> +        policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
>>>>                               GFP_KERNEL);
>>>>            if (!policy->min_freq_req) {
>>>>                ret = -ENOMEM;
>>>>                goto out_destroy_policy;
>>>>            }
>>>>    +        if (policy->boost_supported) {
>>>> +            policy->boost_freq_req = policy->min_freq_req + 2;
>>>> +
>>>> +            ret = freq_qos_add_request(&policy->constraints,
>>>> +                           policy->boost_freq_req,
>>>> +                           FREQ_QOS_MAX,
>>>> +                           policy->cpuinfo.max_freq);
>>>> +            if (ret < 0) {
>>>> +                policy->boost_freq_req = NULL;
>>>> +                goto out_destroy_policy;
>>>> +            }
>>>> +        }
>>>> +
>>>>            ret = freq_qos_add_request(&policy->constraints,
>>>>                           policy->min_freq_req, FREQ_QOS_MIN,
>>>>                           FREQ_QOS_MIN_DEFAULT_VALUE);
>>>>            if (ret < 0) {
>>>> -            /*
>>>> -             * So we don't call freq_qos_remove_request() for an
>>>> -             * uninitialized request.
>>>> -             */
>>>>                kfree(policy->min_freq_req);
>>>>                policy->min_freq_req = NULL;
>>>>                goto out_destroy_policy;
>>>
>>> Hi Pierre, Viresh,
>>>
>>> Sorry for the late follow-up on v8. While re-reading the patch, I
>>> noticed a potential UAF issue on an error path — I might be missing
>>> something, so I'd appreciate a double-check.
>>>
>>> min_freq_req, max_freq_req and boost_freq_req all point into the same
>>> contiguous kzalloc'd block:
>>>
>>> slot0 (min_freq_req + 0) -> min_freq_req
>>> slot1 (min_freq_req + 1) -> max_freq_req
>>> slot2 (min_freq_req + 2) -> boost_freq_req
>>>
>>> If boost_freq_req is successfully added to the QoS constraints list, but
>>> the subsequent freq_qos_add_request() for min_freq_req fails, the error
>>> path does:
>>>
>>> kfree(policy->min_freq_req); /* frees the entire block, including slot2
>>> */
>>> policy->min_freq_req = NULL;
>>> goto out_destroy_policy;
>>>
>>> policy->boost_freq_req is not set to NULL here, so it becomes a dangling
>>> pointer into freed memory.
>>> cpufreq_policy_free() is then called from cpufreq_online() and does:
>>>
>>> freq_qos_remove_request(policy->boost_freq_req); /* UAF */
>>> or this boost qos req will leak.
>>>
>>
>> Good catch!
>>
>> How about remove the kfree() here and just leave it to
>> cpufreq_policy_free()?
>>
> 
> Thanks for the suggestion — this is another fix approach we can
> explore, but there seems to be a small caveat.
> 
> Some additional changes would still be needed; otherwise, removing the
> kfree() here and deferring it to cpufreq_policy_free() can lead to a
> warning.
> 
> The reason is that we neither free policy->min_freq_req nor set policy
> ->min_freq_req = NULL. As a result, when cpufreq_policy_free() later
> calls freq_qos_remove_request(policy->min_freq_req), it hits the
> following warning:
> 
> if (WARN(!freq_qos_request_active(req),
>     "%s() called for unknown object\n", __func__))
>     return -EINVAL;
> 

Therefore, it seems the only option is to allocate memory separately for
boost_freq_req.

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Zhongqiu Han]

On 3/30/2026 3:16 PM, zhenglifeng (A) wrote:
> On 3/30/2026 12:00 PM, Zhongqiu Han wrote:
>> On 3/30/2026 10:10 AM, zhenglifeng (A) wrote:
>>> On 3/29/2026 5:00 PM, Zhongqiu Han wrote:
>>>>> @@ -1377,6 +1386,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
>>>>>         }
>>>>>           freq_qos_remove_request(policy->min_freq_req);
>>>>> +    freq_qos_remove_request(policy->boost_freq_req);
>>>>>         kfree(policy->min_freq_req);
>>>>>           cpufreq_policy_put_kobj(policy);
>>>>> @@ -1445,26 +1455,38 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
>>>>>         cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
>>>>>           if (new_policy) {
>>>>> +        unsigned int count;
>>>>> +
>>>>>             for_each_cpu(j, policy->related_cpus) {
>>>>>                 per_cpu(cpufreq_cpu_data, j) = policy;
>>>>>                 add_cpu_dev_symlink(policy, j, get_cpu_device(j));
>>>>>             }
>>>>>     -        policy->min_freq_req = kzalloc(2 * sizeof(*policy->min_freq_req),
>>>>> +        count = policy->boost_supported ? 3 : 2;
>>>>> +        policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
>>>>>                                GFP_KERNEL);
>>>>>             if (!policy->min_freq_req) {
>>>>>                 ret = -ENOMEM;
>>>>>                 goto out_destroy_policy;
>>>>>             }
>>>>>     +        if (policy->boost_supported) {
>>>>> +            policy->boost_freq_req = policy->min_freq_req + 2;
>>>>> +
>>>>> +            ret = freq_qos_add_request(&policy->constraints,
>>>>> +                           policy->boost_freq_req,
>>>>> +                           FREQ_QOS_MAX,
>>>>> +                           policy->cpuinfo.max_freq);
>>>>> +            if (ret < 0) {
>>>>> +                policy->boost_freq_req = NULL;
>>>>> +                goto out_destroy_policy;
>>>>> +            }
>>>>> +        }
>>>>> +
>>>>>             ret = freq_qos_add_request(&policy->constraints,
>>>>>                            policy->min_freq_req, FREQ_QOS_MIN,
>>>>>                            FREQ_QOS_MIN_DEFAULT_VALUE);
>>>>>             if (ret < 0) {
>>>>> -            /*
>>>>> -             * So we don't call freq_qos_remove_request() for an
>>>>> -             * uninitialized request.
>>>>> -             */
>>>>>                 kfree(policy->min_freq_req);
>>>>>                 policy->min_freq_req = NULL;
>>>>>                 goto out_destroy_policy;
>>>>
>>>> Hi Pierre, Viresh,
>>>>
>>>> Sorry for the late follow-up on v8. While re-reading the patch, I
>>>> noticed a potential UAF issue on an error path — I might be missing
>>>> something, so I'd appreciate a double-check.
>>>>
>>>> min_freq_req, max_freq_req and boost_freq_req all point into the same
>>>> contiguous kzalloc'd block:
>>>>
>>>> slot0 (min_freq_req + 0) -> min_freq_req
>>>> slot1 (min_freq_req + 1) -> max_freq_req
>>>> slot2 (min_freq_req + 2) -> boost_freq_req
>>>>
>>>> If boost_freq_req is successfully added to the QoS constraints list, but
>>>> the subsequent freq_qos_add_request() for min_freq_req fails, the error
>>>> path does:
>>>>
>>>> kfree(policy->min_freq_req); /* frees the entire block, including slot2
>>>> */
>>>> policy->min_freq_req = NULL;
>>>> goto out_destroy_policy;
>>>>
>>>> policy->boost_freq_req is not set to NULL here, so it becomes a dangling
>>>> pointer into freed memory.
>>>> cpufreq_policy_free() is then called from cpufreq_online() and does:
>>>>
>>>> freq_qos_remove_request(policy->boost_freq_req); /* UAF */
>>>> or this boost qos req will leak.
>>>>
>>>
>>> Good catch!
>>>
>>> How about remove the kfree() here and just leave it to
>>> cpufreq_policy_free()?
>>>
>>
>> Thanks for the suggestion — this is another fix approach we can
>> explore, but there seems to be a small caveat.
>>
>> Some additional changes would still be needed; otherwise, removing the
>> kfree() here and deferring it to cpufreq_policy_free() can lead to a
>> warning.
>>
>> The reason is that we neither free policy->min_freq_req nor set policy
>> ->min_freq_req = NULL. As a result, when cpufreq_policy_free() later
>> calls freq_qos_remove_request(policy->min_freq_req), it hits the
>> following warning:
>>
>> if (WARN(!freq_qos_request_active(req),
>>      "%s() called for unknown object\n", __func__))
>>      return -EINVAL;
>>
> 
> Therefore, it seems the only option is to allocate memory separately for
> boost_freq_req.
> 

Thanks Lifeng. Allocating memory separately could also be a direction we
can explore. I also sketched another small example in a separate mail
thread for discussion.


-- 
Thx and BRs,
Zhongqiu Han

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Viresh Kumar]

On 29-03-26, 17:00, Zhongqiu Han wrote:
> Sorry for the late follow-up on v8. While re-reading the patch, I
> noticed a potential UAF issue on an error path — I might be missing
> something, so I'd appreciate a double-check.
> 
> min_freq_req, max_freq_req and boost_freq_req all point into the same
> contiguous kzalloc'd block:
> 
> slot0 (min_freq_req + 0) -> min_freq_req
> slot1 (min_freq_req + 1) -> max_freq_req
> slot2 (min_freq_req + 2) -> boost_freq_req
> 
> If boost_freq_req is successfully added to the QoS constraints list, but
> the subsequent freq_qos_add_request() for min_freq_req fails, the error
> path does:
> 
> kfree(policy->min_freq_req); /* frees the entire block, including slot2
> */
> policy->min_freq_req = NULL;
> goto out_destroy_policy;
> 
> policy->boost_freq_req is not set to NULL here, so it becomes a dangling
> pointer into freed memory.

Nice catch.

The right solution to this I guess is to do kfree and setting min_freq_req to
NULL if boost_freq_req fails (just like what happens in min_freq_req failure
now) and then for later failures, don't do kfree at all but just set the failed
qos feature to NULL (like what is done for max_freq_req now).

-- 
viresh

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Zhongqiu Han]

On 3/30/2026 1:20 PM, Viresh Kumar wrote:
> On 29-03-26, 17:00, Zhongqiu Han wrote:
>> Sorry for the late follow-up on v8. While re-reading the patch, I
>> noticed a potential UAF issue on an error path — I might be missing
>> something, so I'd appreciate a double-check.
>>
>> min_freq_req, max_freq_req and boost_freq_req all point into the same
>> contiguous kzalloc'd block:
>>
>> slot0 (min_freq_req + 0) -> min_freq_req
>> slot1 (min_freq_req + 1) -> max_freq_req
>> slot2 (min_freq_req + 2) -> boost_freq_req
>>
>> If boost_freq_req is successfully added to the QoS constraints list, but
>> the subsequent freq_qos_add_request() for min_freq_req fails, the error
>> path does:
>>
>> kfree(policy->min_freq_req); /* frees the entire block, including slot2
>> */
>> policy->min_freq_req = NULL;
>> goto out_destroy_policy;
>>
>> policy->boost_freq_req is not set to NULL here, so it becomes a dangling
>> pointer into freed memory.
> 
> Nice catch.
> 
> The right solution to this I guess is to do kfree and setting min_freq_req to
> NULL if boost_freq_req fails (just like what happens in min_freq_req failure
> now) and then for later failures, don't do kfree at all but just set the failed
> qos feature to NULL (like what is done for max_freq_req now).
> 


Thanks Viresh — agreed, that approach makes sense.
I sketched a small example along those lines for discussion only if
needed: add boost_freq_req early when boost_supported, free the shared
allocation if that add fails, and on later failures just unwind without
freeing the block.


+ count = policy->boost_supported ? 3 : 2;
+ policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
                                  GFP_KERNEL);
   if (!policy->min_freq_req) {
           ret = -ENOMEM;
           goto out_destroy_policy;
   }

+ if (policy->boost_supported) {
+         policy->boost_freq_req = policy->min_freq_req + 2;
+
+         ret = freq_qos_add_request(&policy->constraints,
+                                    policy->boost_freq_req,
+                                    FREQ_QOS_MAX,
+                                    policy->cpuinfo.max_freq);
+         if (ret < 0) {
+                 policy->boost_freq_req = NULL;
+                 kfree(policy->min_freq_req);
+                 policy->min_freq_req = NULL;
+                 goto out_destroy_policy;
+         }
+ }
+
   ret = freq_qos_add_request(&policy->constraints,
                              policy->min_freq_req, FREQ_QOS_MIN,
                              FREQ_QOS_MIN_DEFAULT_VALUE);
   if (ret < 0) {
-         /*
-          * So we don't call freq_qos_remove_request() for an
-          * uninitialized request.
-          */
+         if (policy->boost_freq_req) {
+                 freq_qos_remove_request(policy->boost_freq_req);
+                 policy->boost_freq_req = NULL;
+         }
           kfree(policy->min_freq_req);
           policy->min_freq_req = NULL;
           goto out_destroy_policy;



-- 
Thx and BRs,
Zhongqiu Han

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Zhongqiu Han]

On 3/30/2026 8:55 PM, Zhongqiu Han wrote:
> On 3/30/2026 1:20 PM, Viresh Kumar wrote:
>> On 29-03-26, 17:00, Zhongqiu Han wrote:
>>> Sorry for the late follow-up on v8. While re-reading the patch, I
>>> noticed a potential UAF issue on an error path — I might be missing
>>> something, so I'd appreciate a double-check.
>>>
>>> min_freq_req, max_freq_req and boost_freq_req all point into the same
>>> contiguous kzalloc'd block:
>>>
>>> slot0 (min_freq_req + 0) -> min_freq_req
>>> slot1 (min_freq_req + 1) -> max_freq_req
>>> slot2 (min_freq_req + 2) -> boost_freq_req
>>>
>>> If boost_freq_req is successfully added to the QoS constraints list, but
>>> the subsequent freq_qos_add_request() for min_freq_req fails, the error
>>> path does:
>>>
>>> kfree(policy->min_freq_req); /* frees the entire block, including slot2
>>> */
>>> policy->min_freq_req = NULL;
>>> goto out_destroy_policy;
>>>
>>> policy->boost_freq_req is not set to NULL here, so it becomes a dangling
>>> pointer into freed memory.
>>
>> Nice catch.
>>
>> The right solution to this I guess is to do kfree and setting 
>> min_freq_req to
>> NULL if boost_freq_req fails (just like what happens in min_freq_req 
>> failure
>> now) and then for later failures, don't do kfree at all but just set 
>> the failed
>> qos feature to NULL (like what is done for max_freq_req now).
>>
> 
> 
> Thanks Viresh — agreed, that approach makes sense.
> I sketched a small example along those lines for discussion only if
> needed: add boost_freq_req early when boost_supported, free the shared
> allocation if that add fails, and on later failures just unwind without
> freeing the block.
> 
> 
> + count = policy->boost_supported ? 3 : 2;
> + policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
>                                   GFP_KERNEL);
>    if (!policy->min_freq_req) {
>            ret = -ENOMEM;
>            goto out_destroy_policy;
>    }
> 
> + if (policy->boost_supported) {
> +         policy->boost_freq_req = policy->min_freq_req + 2;
> +
> +         ret = freq_qos_add_request(&policy->constraints,
> +                                    policy->boost_freq_req,
> +                                    FREQ_QOS_MAX,
> +                                    policy->cpuinfo.max_freq);
> +         if (ret < 0) {
> +                 policy->boost_freq_req = NULL;
> +                 kfree(policy->min_freq_req);
> +                 policy->min_freq_req = NULL;
> +                 goto out_destroy_policy;
> +         }
> + }
> +
>    ret = freq_qos_add_request(&policy->constraints,
>                               policy->min_freq_req, FREQ_QOS_MIN,
>                               FREQ_QOS_MIN_DEFAULT_VALUE);
>    if (ret < 0) {
> -         /*
> -          * So we don't call freq_qos_remove_request() for an
> -          * uninitialized request.
> -          */
> +         if (policy->boost_freq_req) {
> +                 freq_qos_remove_request(policy->boost_freq_req);
> +                 policy->boost_freq_req = NULL;
> +         }
>            kfree(policy->min_freq_req);
>            policy->min_freq_req = NULL;
>            goto out_destroy_policy;
> 
> 
> 

Now that the patch has been picked on queue, if the approach in the
current draft looks reasonable, I'm happy to send it out as a proper
fixup.

-- 
Thx and BRs,
Zhongqiu Han

Re: [PATCH v8 2/2] cpufreq: Add boost_freq_req QoS request

[Viresh Kumar]

On 30-03-26, 20:55, Zhongqiu Han wrote:
> Thanks Viresh — agreed, that approach makes sense.
> I sketched a small example along those lines for discussion only if
> needed: add boost_freq_req early when boost_supported, free the shared
> allocation if that add fails, and on later failures just unwind without
> freeing the block.

I have taken a different approach to fix this. (Build tested).

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index c0aa970c7a67..f4a949f1e48f 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -614,7 +614,7 @@ static int policy_set_boost(struct cpufreq_policy *policy, bool enable)
                return ret;
        }
 
-       ret = freq_qos_update_request(policy->boost_freq_req, policy->cpuinfo.max_freq);
+       ret = freq_qos_update_request(&policy->boost_freq_req, policy->cpuinfo.max_freq);
        if (ret < 0) {
                policy->boost_enabled = !policy->boost_enabled;
                cpufreq_driver->set_boost(policy, policy->boost_enabled);
@@ -769,7 +769,7 @@ static ssize_t store_##file_name                                    \
        if (ret)                                                        \
                return ret;                                             \
                                                                        \
-       ret = freq_qos_update_request(policy->object##_freq_req, val);\
+       ret = freq_qos_update_request(&policy->object##_freq_req, val); \
        return ret >= 0 ? count : ret;                                  \
 }
 
@@ -1374,7 +1374,7 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
        /* Cancel any pending policy->update work before freeing the policy. */
        cancel_work_sync(&policy->update);
 
-       if (policy->max_freq_req) {
+       if (freq_qos_request_active(&policy->max_freq_req)) {
                /*
                 * Remove max_freq_req after sending CPUFREQ_REMOVE_POLICY
                 * notification, since CPUFREQ_CREATE_POLICY notification was
@@ -1382,12 +1382,13 @@ static void cpufreq_policy_free(struct cpufreq_policy *policy)
                 */
                blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                                             CPUFREQ_REMOVE_POLICY, policy);
-               freq_qos_remove_request(policy->max_freq_req);
+               freq_qos_remove_request(&policy->max_freq_req);
        }
 
-       freq_qos_remove_request(policy->min_freq_req);
-       freq_qos_remove_request(policy->boost_freq_req);
-       kfree(policy->min_freq_req);
+       if (freq_qos_request_active(&policy->min_freq_req))
+               freq_qos_remove_request(&policy->min_freq_req);
+       if (freq_qos_request_active(&policy->boost_freq_req))
+               freq_qos_remove_request(&policy->boost_freq_req);
 
        cpufreq_policy_put_kobj(policy);
        free_cpumask_var(policy->real_cpus);
@@ -1452,57 +1453,31 @@ static int cpufreq_policy_online(struct cpufreq_policy *policy,
        cpumask_and(policy->cpus, policy->cpus, cpu_online_mask);
 
        if (new_policy) {
-               unsigned int count;
-
                for_each_cpu(j, policy->related_cpus) {
                        per_cpu(cpufreq_cpu_data, j) = policy;
                        add_cpu_dev_symlink(policy, j, get_cpu_device(j));
                }
 
-               count = policy->boost_supported ? 3 : 2;
-               policy->min_freq_req = kzalloc(count * sizeof(*policy->min_freq_req),
-                                              GFP_KERNEL);
-               if (!policy->min_freq_req) {
-                       ret = -ENOMEM;
-                       goto out_destroy_policy;
-               }
-
                if (policy->boost_supported) {
-                       policy->boost_freq_req = policy->min_freq_req + 2;
-
                        ret = freq_qos_add_request(&policy->constraints,
-                                                  policy->boost_freq_req,
+                                                  &policy->boost_freq_req,
                                                   FREQ_QOS_MAX,
                                                   policy->cpuinfo.max_freq);
-                       if (ret < 0) {
-                               policy->boost_freq_req = NULL;
+                       if (ret < 0)
                                goto out_destroy_policy;
-                       }
                }
 
                ret = freq_qos_add_request(&policy->constraints,
-                                          policy->min_freq_req, FREQ_QOS_MIN,
+                                          &policy->min_freq_req, FREQ_QOS_MIN,
                                           FREQ_QOS_MIN_DEFAULT_VALUE);
-               if (ret < 0) {
-                       kfree(policy->min_freq_req);
-                       policy->min_freq_req = NULL;
+               if (ret < 0)
                        goto out_destroy_policy;
-               }
-
-               /*
-                * This must be initialized right here to avoid calling
-                * freq_qos_remove_request() on uninitialized request in case
-                * of errors.
-                */
-               policy->max_freq_req = policy->min_freq_req + 1;
 
                ret = freq_qos_add_request(&policy->constraints,
-                                          policy->max_freq_req, FREQ_QOS_MAX,
+                                          &policy->max_freq_req, FREQ_QOS_MAX,
                                           FREQ_QOS_MAX_DEFAULT_VALUE);
-               if (ret < 0) {
-                       policy->max_freq_req = NULL;
+               if (ret < 0)
                        goto out_destroy_policy;
-               }
 
                blocking_notifier_call_chain(&cpufreq_policy_notifier_list,
                                CPUFREQ_CREATE_POLICY, policy);
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index b6f6c7d06912..9b10eb486ece 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -79,9 +79,9 @@ struct cpufreq_policy {
                                         * called, but you're in IRQ context */
 
        struct freq_constraints constraints;
-       struct freq_qos_request *min_freq_req;
-       struct freq_qos_request *max_freq_req;
-       struct freq_qos_request *boost_freq_req;
+       struct freq_qos_request min_freq_req;
+       struct freq_qos_request max_freq_req;
+       struct freq_qos_request boost_freq_req;
 
        struct cpufreq_frequency_table  *freq_table;
        enum cpufreq_table_sorting freq_table_sorted;

-- 
viresh

Re: [PATCH v8 0/2] cpufreq: Introduce boost frequency QoS

[Viresh Kumar]

On 26-03-26, 21:43, Pierre Gondois wrote:
> Pierre Gondois (2):
>   cpufreq: Remove max_freq_req update for pre-existing policy
>   cpufreq: Add boost_freq_req QoS request
> 
>  drivers/cpufreq/amd-pstate.c   |  2 --
>  drivers/cpufreq/cppc_cpufreq.c | 10 ++-----
>  drivers/cpufreq/cpufreq.c      | 50 +++++++++++++++++++++-------------
>  include/linux/cpufreq.h        |  1 +
>  4 files changed, 34 insertions(+), 29 deletions(-)

Thanks Pierre for your patience.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

Re: [PATCH v8 0/2] cpufreq: Introduce boost frequency QoS

[Pierre Gondois]

On 3/27/26 04:43, Viresh Kumar wrote:
> On 26-03-26, 21:43, Pierre Gondois wrote:
>> Pierre Gondois (2):
>>    cpufreq: Remove max_freq_req update for pre-existing policy
>>    cpufreq: Add boost_freq_req QoS request
>>
>>   drivers/cpufreq/amd-pstate.c   |  2 --
>>   drivers/cpufreq/cppc_cpufreq.c | 10 ++-----
>>   drivers/cpufreq/cpufreq.c      | 50 +++++++++++++++++++++-------------
>>   include/linux/cpufreq.h        |  1 +
>>   4 files changed, 34 insertions(+), 29 deletions(-)
> Thanks Pierre for your patience.
Thanks for the review (to Lifeng aswell)
>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
>

Re: [PATCH v8 0/2] cpufreq: Introduce boost frequency QoS

[Rafael J. Wysocki]

On Fri, Mar 27, 2026 at 5:09 PM Pierre Gondois <pierre.gondois@arm.com> wrote:
>
>
> On 3/27/26 04:43, Viresh Kumar wrote:
> > On 26-03-26, 21:43, Pierre Gondois wrote:
> >> Pierre Gondois (2):
> >>    cpufreq: Remove max_freq_req update for pre-existing policy
> >>    cpufreq: Add boost_freq_req QoS request
> >>
> >>   drivers/cpufreq/amd-pstate.c   |  2 --
> >>   drivers/cpufreq/cppc_cpufreq.c | 10 ++-----
> >>   drivers/cpufreq/cpufreq.c      | 50 +++++++++++++++++++++-------------
> >>   include/linux/cpufreq.h        |  1 +
> >>   4 files changed, 34 insertions(+), 29 deletions(-)
> > Thanks Pierre for your patience.
> Thanks for the review (to Lifeng aswell)
> >
> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Applied as 7.1 material, thanks!