drivers/base/cpu.c | 5 +- include/linux/pm_qos.h | 5 ++ kernel/power/qos.c | 147 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 155 insertions(+), 2 deletions(-)
Users currently lack a mechanism to define granular, per-CPU PM QoS
resume latency constraints during the early boot phase.
While the idle=poll boot parameter exists, it enforces a global
override, forcing all CPUs in the system to "poll". This global approach
is not suitable for asymmetric workloads where strict latency guarantees
are required only on specific critical CPUs, while housekeeping or
non-critical CPUs should be allowed to enter deeper power states to save
energy.
Additionally, the existing sysfs interface
(/sys/devices/system/cpu/cpuN/power/pm_qos_resume_latency_us) becomes
available only after userspace initialisation. This is too late to
prevent deep C-state entry during the early kernel boot phase, which may
be required for debugging early boot hangs related to C-state
transitions or for workloads requiring strict latency guarantees
immediately upon system start.
This patch introduces the pm_qos_resume_latency_us kernel boot
parameter, which allows users to specify distinct resume latency
constraints for specific CPU ranges.
Syntax: pm_qos_resume_latency_us=range:value,range:value...
Unlike the sysfs interface which accepts the special string "n/a" to
remove a constraint, this boot parameter strictly requires integer
values. The special value "n/a" is not supported; the integer 0 must be
used to represent a 0 us latency constraint (polling).
For example:
"pm_qos_resume_latency_us=0:0,1-15:20"
Forces CPU 0 to poll on idle; constrains CPUs 1-15 to not enter a sleep
state that takes longer than 20 us to wake up. All other CPUs will have
the default (no resume latency) applied.
Implementation Details:
- The parameter string is captured via __setup() and parsed in
an early_initcall() to ensure suitable memory allocators are
available.
- Constraints are stored in a read-only linked list.
- The constraints are queried and applied in register_cpu().
This ensures the latency requirement is active immediately
upon CPU registration, effectively acting as a "birth"
constraint before the cpuidle governor takes over.
- The parsing logic enforces a "First Match Wins" policy: if a
CPU falls into multiple specified ranges, the latency value
from the first matching entry is used.
- The constraints persist across CPU hotplug events.
Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
---
drivers/base/cpu.c | 5 +-
include/linux/pm_qos.h | 5 ++
kernel/power/qos.c | 147 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 155 insertions(+), 2 deletions(-)
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index c6c57b6f61c6..1dea5bcd76a0 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -416,6 +416,7 @@ EXPORT_SYMBOL_GPL(cpu_subsys);
int register_cpu(struct cpu *cpu, int num)
{
int error;
+ s32 resume_latency;
cpu->node_id = cpu_to_node(num);
memset(&cpu->dev, 0x00, sizeof(struct device));
@@ -436,8 +437,8 @@ int register_cpu(struct cpu *cpu, int num)
per_cpu(cpu_sys_devices, num) = &cpu->dev;
register_cpu_under_node(num, cpu_to_node(num));
- dev_pm_qos_expose_latency_limit(&cpu->dev,
- PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
+ resume_latency = pm_qos_get_boot_cpu_latency_limit(num);
+ dev_pm_qos_expose_latency_limit(&cpu->dev, resume_latency);
set_cpu_enabled(num, true);
return 0;
diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 6cea4455f867..556a7dff1419 100644
--- a/include/linux/pm_qos.h
+++ b/include/linux/pm_qos.h
@@ -174,6 +174,7 @@ static inline s32 cpu_wakeup_latency_qos_limit(void)
#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);
+s32 pm_qos_get_boot_cpu_latency_limit(unsigned int cpu);
s32 __dev_pm_qos_resume_latency(struct device *dev);
s32 dev_pm_qos_read_value(struct device *dev, enum dev_pm_qos_req_type type);
int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
@@ -218,6 +219,10 @@ static inline s32 dev_pm_qos_raw_resume_latency(struct device *dev)
pm_qos_read_value(&dev->power.qos->resume_latency);
}
#else
+static inline s32 pm_qos_get_boot_cpu_latency_limit(unsigned int cpu)
+{
+ return PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
+}
static inline enum pm_qos_flags_status __dev_pm_qos_flags(struct device *dev,
s32 mask)
{ return PM_QOS_FLAGS_UNDEFINED; }
diff --git a/kernel/power/qos.c b/kernel/power/qos.c
index f7d8064e9adc..6a12f1143358 100644
--- a/kernel/power/qos.c
+++ b/kernel/power/qos.c
@@ -34,6 +34,11 @@
#include <linux/kernel.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
+#include <linux/cpumask.h>
+#include <linux/cpu.h>
+#include <linux/list.h>
+
+#include <asm/setup.h>
#include <linux/uaccess.h>
#include <linux/export.h>
@@ -46,6 +51,10 @@
*/
static DEFINE_SPINLOCK(pm_qos_lock);
+static LIST_HEAD(pm_qos_boot_list);
+
+static char pm_qos_resume_latency_cmdline[COMMAND_LINE_SIZE] __initdata;
+
/**
* pm_qos_read_value - Return the current effective constraint value.
* @c: List of PM QoS constraint requests.
@@ -220,6 +229,144 @@ static struct pm_qos_constraints cpu_latency_constraints = {
.type = PM_QOS_MIN,
};
+struct pm_qos_boot_entry {
+ struct list_head node;
+ struct cpumask mask;
+ s32 latency;
+};
+
+static int __init pm_qos_latency_us_setup(char *str)
+{
+ strscpy(pm_qos_resume_latency_cmdline, str,
+ sizeof(pm_qos_resume_latency_cmdline));
+ return 1;
+}
+__setup("pm_qos_resume_latency_us=", pm_qos_latency_us_setup);
+
+/* init_pm_qos_latency_us_setup - Parse the pm_qos_latency_us boot parameter.
+ *
+ * Parses the kernel command line option "pm_qos_resume_latency_us=" to establish
+ * per-CPU resume latency constraints. These constraints are applied
+ * immediately when a CPU is registered.
+ *
+ * Syntax: pm_qos_resume_latency_us=<cpu-list>:<value>[,<cpu-list>:<value>...]
+ * Example: pm_qos_resume_latency_us=0-3:0,4-7:20
+ *
+ * The parsing logic enforces a "First Match Wins" policy. If a CPU is
+ * covered by multiple entries in the list, only the first valid entry
+ * applies. Any subsequent overlapping ranges for that CPU are ignored.
+ *
+ * Return: 0 on success, or a negative error code on failure.
+ */
+static int __init init_pm_qos_latency_us_setup(void)
+{
+ char *token, *cmd = pm_qos_resume_latency_cmdline;
+ struct pm_qos_boot_entry *entry, *tentry;
+ cpumask_var_t covered;
+ int ret;
+
+ if (boot_option_idle_override == IDLE_POLL) {
+ pr_warn("pm_qos: Cannot be used with idle=poll\n");
+ return -EINVAL;
+ }
+
+ if (!zalloc_cpumask_var(&covered, GFP_KERNEL)) {
+ pr_warn("pm_qos: Failed to allocate memory for parsing boot parameter\n");
+ return -ENOMEM;
+ }
+
+ while ((token = strsep(&cmd, ",")) != NULL) {
+ char *str_range, *str_val;
+
+ str_range = strsep(&token, ":");
+ str_val = token;
+
+ if (!str_val) {
+ pr_warn("pm_qos: Missing value range %s\n",
+ str_range);
+ continue;
+ }
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ pr_warn("pm_qos: Failed to allocate memory for boot entry\n");
+ goto cleanup;
+ }
+
+ if (cpulist_parse(str_range, &entry->mask)) {
+ pr_warn("pm_qos: Failed to parse cpulist range %s\n",
+ str_range);
+ kfree(entry);
+ continue;
+ }
+
+ cpumask_andnot(&entry->mask, &entry->mask, covered);
+ if (cpumask_empty(&entry->mask)) {
+ pr_warn("pm_qos: Entry %s already covered, ignoring\n",
+ str_range);
+ kfree(entry);
+ continue;
+ }
+ cpumask_or(covered, covered, &entry->mask);
+
+ if (kstrtos32(str_val, 0, &entry->latency)) {
+ pr_warn("pm_qos: Invalid latency requirement value %s\n",
+ str_val);
+ kfree(entry);
+ continue;
+ }
+
+ if (entry->latency < 0) {
+ pr_warn("pm_qos: Latency requirement cannot be negative: %d\n",
+ entry->latency);
+ kfree(entry);
+ continue;
+ }
+
+ list_add_tail(&entry->node, &pm_qos_boot_list);
+ }
+
+ free_cpumask_var(covered);
+ return 0;
+
+cleanup:
+ list_for_each_entry_safe(entry, tentry, &pm_qos_boot_list, node) {
+ list_del(&entry->node);
+ kfree(entry);
+ }
+
+ free_cpumask_var(covered);
+ return ret;
+}
+early_initcall(init_pm_qos_latency_us_setup);
+
+/**
+ * pm_qos_get_boot_cpu_latency_limit - Get boot-time latency limit for a CPU.
+ * @cpu: Logical CPU number to check.
+ *
+ * Checks the read-only boot-time constraints list to see if a specific
+ * PM QoS latency override was requested for this CPU via the kernel
+ * command line.
+ *
+ * Return: The latency limit in microseconds if a constraint exists,
+ * or PM_QOS_RESUME_LATENCY_NO_CONSTRAINT if no boot override applies.
+ */
+s32 pm_qos_get_boot_cpu_latency_limit(unsigned int cpu)
+{
+ struct pm_qos_boot_entry *entry;
+
+ if (list_empty(&pm_qos_boot_list))
+ return PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
+
+ list_for_each_entry(entry, &pm_qos_boot_list, node) {
+ if (cpumask_test_cpu(cpu, &entry->mask))
+ return entry->latency;
+ }
+
+ return PM_QOS_RESUME_LATENCY_NO_CONSTRAINT;
+}
+EXPORT_SYMBOL_GPL(pm_qos_get_boot_cpu_latency_limit);
+
static inline bool cpu_latency_qos_value_invalid(s32 value)
{
return value < 0 && value != PM_QOS_DEFAULT_VALUE;
--
2.51.0Hi Aaron,
kernel test robot noticed the following build errors:
[auto build test ERROR on driver-core/driver-core-testing]
[also build test ERROR on driver-core/driver-core-next driver-core/driver-core-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master amd-pstate/linux-next amd-pstate/bleeding-edge v6.19-rc6 next-20260122]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Aaron-Tomlin/PM-QoS-Introduce-boot-parameter-pm_qos_resume_latency_us/20260123-090409
base: driver-core/driver-core-testing
patch link: https://lore.kernel.org/r/20260123010024.3301276-1-atomlin%40atomlin.com
patch subject: [PATCH] PM: QoS: Introduce boot parameter pm_qos_resume_latency_us
config: arm64-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260123/202601231132.HoRpyfUy-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project f43d6834093b19baf79beda8c0337ab020ac5f17)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260123/202601231132.HoRpyfUy-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601231132.HoRpyfUy-lkp@intel.com/
All errors (new ones prefixed by >>):
>> kernel/power/qos.c:268:6: error: use of undeclared identifier 'boot_option_idle_override'
268 | if (boot_option_idle_override == IDLE_POLL) {
| ^~~~~~~~~~~~~~~~~~~~~~~~~
>> kernel/power/qos.c:268:35: error: use of undeclared identifier 'IDLE_POLL'; did you mean 'SIL_POLL'?
268 | if (boot_option_idle_override == IDLE_POLL) {
| ^~~~~~~~~
| SIL_POLL
./include/linux/signal.h:42:2: note: 'SIL_POLL' declared here
42 | SIL_POLL,
| ^
kernel/power/qos.c:354:5: error: redefinition of 'pm_qos_get_boot_cpu_latency_limit'
354 | s32 pm_qos_get_boot_cpu_latency_limit(unsigned int cpu)
| ^
./include/linux/pm_qos.h:222:19: note: previous definition is here
222 | static inline s32 pm_qos_get_boot_cpu_latency_limit(unsigned int cpu)
| ^
3 errors generated.
vim +/boot_option_idle_override +268 kernel/power/qos.c
245
246 /* init_pm_qos_latency_us_setup - Parse the pm_qos_latency_us boot parameter.
247 *
248 * Parses the kernel command line option "pm_qos_resume_latency_us=" to establish
249 * per-CPU resume latency constraints. These constraints are applied
250 * immediately when a CPU is registered.
251 *
252 * Syntax: pm_qos_resume_latency_us=<cpu-list>:<value>[,<cpu-list>:<value>...]
253 * Example: pm_qos_resume_latency_us=0-3:0,4-7:20
254 *
255 * The parsing logic enforces a "First Match Wins" policy. If a CPU is
256 * covered by multiple entries in the list, only the first valid entry
257 * applies. Any subsequent overlapping ranges for that CPU are ignored.
258 *
259 * Return: 0 on success, or a negative error code on failure.
260 */
261 static int __init init_pm_qos_latency_us_setup(void)
262 {
263 char *token, *cmd = pm_qos_resume_latency_cmdline;
264 struct pm_qos_boot_entry *entry, *tentry;
265 cpumask_var_t covered;
266 int ret;
267
> 268 if (boot_option_idle_override == IDLE_POLL) {
269 pr_warn("pm_qos: Cannot be used with idle=poll\n");
270 return -EINVAL;
271 }
272
273 if (!zalloc_cpumask_var(&covered, GFP_KERNEL)) {
274 pr_warn("pm_qos: Failed to allocate memory for parsing boot parameter\n");
275 return -ENOMEM;
276 }
277
278 while ((token = strsep(&cmd, ",")) != NULL) {
279 char *str_range, *str_val;
280
281 str_range = strsep(&token, ":");
282 str_val = token;
283
284 if (!str_val) {
285 pr_warn("pm_qos: Missing value range %s\n",
286 str_range);
287 continue;
288 }
289
290 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
291 if (!entry) {
292 pr_warn("pm_qos: Failed to allocate memory for boot entry\n");
293 goto cleanup;
294 }
295
296 if (cpulist_parse(str_range, &entry->mask)) {
297 pr_warn("pm_qos: Failed to parse cpulist range %s\n",
298 str_range);
299 kfree(entry);
300 continue;
301 }
302
303 cpumask_andnot(&entry->mask, &entry->mask, covered);
304 if (cpumask_empty(&entry->mask)) {
305 pr_warn("pm_qos: Entry %s already covered, ignoring\n",
306 str_range);
307 kfree(entry);
308 continue;
309 }
310 cpumask_or(covered, covered, &entry->mask);
311
312 if (kstrtos32(str_val, 0, &entry->latency)) {
313 pr_warn("pm_qos: Invalid latency requirement value %s\n",
314 str_val);
315 kfree(entry);
316 continue;
317 }
318
319 if (entry->latency < 0) {
320 pr_warn("pm_qos: Latency requirement cannot be negative: %d\n",
321 entry->latency);
322 kfree(entry);
323 continue;
324 }
325
326 list_add_tail(&entry->node, &pm_qos_boot_list);
327 }
328
329 free_cpumask_var(covered);
330 return 0;
331
332 cleanup:
333 list_for_each_entry_safe(entry, tentry, &pm_qos_boot_list, node) {
334 list_del(&entry->node);
335 kfree(entry);
336 }
337
338 free_cpumask_var(covered);
339 return ret;
340 }
341 early_initcall(init_pm_qos_latency_us_setup);
342
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Aaron,
kernel test robot noticed the following build warnings:
[auto build test WARNING on driver-core/driver-core-testing]
[also build test WARNING on driver-core/driver-core-next driver-core/driver-core-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master amd-pstate/linux-next amd-pstate/bleeding-edge v6.19-rc6 next-20260122]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Aaron-Tomlin/PM-QoS-Introduce-boot-parameter-pm_qos_resume_latency_us/20260123-090409
base: driver-core/driver-core-testing
patch link: https://lore.kernel.org/r/20260123010024.3301276-1-atomlin%40atomlin.com
patch subject: [PATCH] PM: QoS: Introduce boot parameter pm_qos_resume_latency_us
config: powerpc64-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260123/202601231030.N1gaWeuj-lkp@intel.com/config)
compiler: powerpc64-linux-gcc (GCC) 15.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260123/202601231030.N1gaWeuj-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601231030.N1gaWeuj-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> kernel/power/qos.c:56:13: warning: 'pm_qos_resume_latency_cmdline' defined but not used [-Wunused-variable]
56 | static char pm_qos_resume_latency_cmdline[COMMAND_LINE_SIZE] __initdata;
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
vim +/pm_qos_resume_latency_cmdline +56 kernel/power/qos.c
55
> 56 static char pm_qos_resume_latency_cmdline[COMMAND_LINE_SIZE] __initdata;
57
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Aaron,
kernel test robot noticed the following build errors:
[auto build test ERROR on driver-core/driver-core-testing]
[also build test ERROR on driver-core/driver-core-next driver-core/driver-core-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master amd-pstate/linux-next amd-pstate/bleeding-edge v6.19-rc6 next-20260122]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Aaron-Tomlin/PM-QoS-Introduce-boot-parameter-pm_qos_resume_latency_us/20260123-090409
base: driver-core/driver-core-testing
patch link: https://lore.kernel.org/r/20260123010024.3301276-1-atomlin%40atomlin.com
patch subject: [PATCH] PM: QoS: Introduce boot parameter pm_qos_resume_latency_us
config: arm64-randconfig-r072-20260123 (https://download.01.org/0day-ci/archive/20260123/202601231700.admSdObE-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 8.5.0
smatch version: v0.5.0-8994-gd50c5a4c
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260123/202601231700.admSdObE-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601231700.admSdObE-lkp@intel.com/
All errors (new ones prefixed by >>):
kernel/power/qos.c: In function 'init_pm_qos_latency_us_setup':
>> kernel/power/qos.c:268:6: error: 'boot_option_idle_override' undeclared (first use in this function)
if (boot_option_idle_override == IDLE_POLL) {
^~~~~~~~~~~~~~~~~~~~~~~~~
kernel/power/qos.c:268:6: note: each undeclared identifier is reported only once for each function it appears in
>> kernel/power/qos.c:268:35: error: 'IDLE_POLL' undeclared (first use in this function); did you mean 'SIL_POLL'?
if (boot_option_idle_override == IDLE_POLL) {
^~~~~~~~~
SIL_POLL
vim +/boot_option_idle_override +268 kernel/power/qos.c
245
246 /* init_pm_qos_latency_us_setup - Parse the pm_qos_latency_us boot parameter.
247 *
248 * Parses the kernel command line option "pm_qos_resume_latency_us=" to establish
249 * per-CPU resume latency constraints. These constraints are applied
250 * immediately when a CPU is registered.
251 *
252 * Syntax: pm_qos_resume_latency_us=<cpu-list>:<value>[,<cpu-list>:<value>...]
253 * Example: pm_qos_resume_latency_us=0-3:0,4-7:20
254 *
255 * The parsing logic enforces a "First Match Wins" policy. If a CPU is
256 * covered by multiple entries in the list, only the first valid entry
257 * applies. Any subsequent overlapping ranges for that CPU are ignored.
258 *
259 * Return: 0 on success, or a negative error code on failure.
260 */
261 static int __init init_pm_qos_latency_us_setup(void)
262 {
263 char *token, *cmd = pm_qos_resume_latency_cmdline;
264 struct pm_qos_boot_entry *entry, *tentry;
265 cpumask_var_t covered;
266 int ret;
267
> 268 if (boot_option_idle_override == IDLE_POLL) {
269 pr_warn("pm_qos: Cannot be used with idle=poll\n");
270 return -EINVAL;
271 }
272
273 if (!zalloc_cpumask_var(&covered, GFP_KERNEL)) {
274 pr_warn("pm_qos: Failed to allocate memory for parsing boot parameter\n");
275 return -ENOMEM;
276 }
277
278 while ((token = strsep(&cmd, ",")) != NULL) {
279 char *str_range, *str_val;
280
281 str_range = strsep(&token, ":");
282 str_val = token;
283
284 if (!str_val) {
285 pr_warn("pm_qos: Missing value range %s\n",
286 str_range);
287 continue;
288 }
289
290 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
291 if (!entry) {
292 pr_warn("pm_qos: Failed to allocate memory for boot entry\n");
293 goto cleanup;
294 }
295
296 if (cpulist_parse(str_range, &entry->mask)) {
297 pr_warn("pm_qos: Failed to parse cpulist range %s\n",
298 str_range);
299 kfree(entry);
300 continue;
301 }
302
303 cpumask_andnot(&entry->mask, &entry->mask, covered);
304 if (cpumask_empty(&entry->mask)) {
305 pr_warn("pm_qos: Entry %s already covered, ignoring\n",
306 str_range);
307 kfree(entry);
308 continue;
309 }
310 cpumask_or(covered, covered, &entry->mask);
311
312 if (kstrtos32(str_val, 0, &entry->latency)) {
313 pr_warn("pm_qos: Invalid latency requirement value %s\n",
314 str_val);
315 kfree(entry);
316 continue;
317 }
318
319 if (entry->latency < 0) {
320 pr_warn("pm_qos: Latency requirement cannot be negative: %d\n",
321 entry->latency);
322 kfree(entry);
323 continue;
324 }
325
326 list_add_tail(&entry->node, &pm_qos_boot_list);
327 }
328
329 free_cpumask_var(covered);
330 return 0;
331
332 cleanup:
333 list_for_each_entry_safe(entry, tentry, &pm_qos_boot_list, node) {
334 list_del(&entry->node);
335 kfree(entry);
336 }
337
338 free_cpumask_var(covered);
339 return ret;
340 }
341 early_initcall(init_pm_qos_latency_us_setup);
342
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Aaron,
kernel test robot noticed the following build warnings:
[auto build test WARNING on driver-core/driver-core-testing]
[also build test WARNING on driver-core/driver-core-next driver-core/driver-core-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master amd-pstate/linux-next amd-pstate/bleeding-edge v6.19-rc6 next-20260122]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Aaron-Tomlin/PM-QoS-Introduce-boot-parameter-pm_qos_resume_latency_us/20260123-090409
base: driver-core/driver-core-testing
patch link: https://lore.kernel.org/r/20260123010024.3301276-1-atomlin%40atomlin.com
patch subject: [PATCH] PM: QoS: Introduce boot parameter pm_qos_resume_latency_us
config: x86_64-randconfig-161-20260123 (https://download.01.org/0day-ci/archive/20260123/202601231616.nbo2ijJf-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
smatch version: v0.5.0-8994-gd50c5a4c
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260123/202601231616.nbo2ijJf-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601231616.nbo2ijJf-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> kernel/power/qos.c:339:9: warning: variable 'ret' is uninitialized when used here [-Wuninitialized]
339 | return ret;
| ^~~
kernel/power/qos.c:266:9: note: initialize the variable 'ret' to silence this warning
266 | int ret;
| ^
| = 0
kernel/power/qos.c:354:5: error: redefinition of 'pm_qos_get_boot_cpu_latency_limit'
354 | s32 pm_qos_get_boot_cpu_latency_limit(unsigned int cpu)
| ^
include/linux/pm_qos.h:222:19: note: previous definition is here
222 | static inline s32 pm_qos_get_boot_cpu_latency_limit(unsigned int cpu)
| ^
1 warning and 1 error generated.
vim +/ret +339 kernel/power/qos.c
245
246 /* init_pm_qos_latency_us_setup - Parse the pm_qos_latency_us boot parameter.
247 *
248 * Parses the kernel command line option "pm_qos_resume_latency_us=" to establish
249 * per-CPU resume latency constraints. These constraints are applied
250 * immediately when a CPU is registered.
251 *
252 * Syntax: pm_qos_resume_latency_us=<cpu-list>:<value>[,<cpu-list>:<value>...]
253 * Example: pm_qos_resume_latency_us=0-3:0,4-7:20
254 *
255 * The parsing logic enforces a "First Match Wins" policy. If a CPU is
256 * covered by multiple entries in the list, only the first valid entry
257 * applies. Any subsequent overlapping ranges for that CPU are ignored.
258 *
259 * Return: 0 on success, or a negative error code on failure.
260 */
261 static int __init init_pm_qos_latency_us_setup(void)
262 {
263 char *token, *cmd = pm_qos_resume_latency_cmdline;
264 struct pm_qos_boot_entry *entry, *tentry;
265 cpumask_var_t covered;
266 int ret;
267
268 if (boot_option_idle_override == IDLE_POLL) {
269 pr_warn("pm_qos: Cannot be used with idle=poll\n");
270 return -EINVAL;
271 }
272
273 if (!zalloc_cpumask_var(&covered, GFP_KERNEL)) {
274 pr_warn("pm_qos: Failed to allocate memory for parsing boot parameter\n");
275 return -ENOMEM;
276 }
277
278 while ((token = strsep(&cmd, ",")) != NULL) {
279 char *str_range, *str_val;
280
281 str_range = strsep(&token, ":");
282 str_val = token;
283
284 if (!str_val) {
285 pr_warn("pm_qos: Missing value range %s\n",
286 str_range);
287 continue;
288 }
289
290 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
291 if (!entry) {
292 pr_warn("pm_qos: Failed to allocate memory for boot entry\n");
293 goto cleanup;
294 }
295
296 if (cpulist_parse(str_range, &entry->mask)) {
297 pr_warn("pm_qos: Failed to parse cpulist range %s\n",
298 str_range);
299 kfree(entry);
300 continue;
301 }
302
303 cpumask_andnot(&entry->mask, &entry->mask, covered);
304 if (cpumask_empty(&entry->mask)) {
305 pr_warn("pm_qos: Entry %s already covered, ignoring\n",
306 str_range);
307 kfree(entry);
308 continue;
309 }
310 cpumask_or(covered, covered, &entry->mask);
311
312 if (kstrtos32(str_val, 0, &entry->latency)) {
313 pr_warn("pm_qos: Invalid latency requirement value %s\n",
314 str_val);
315 kfree(entry);
316 continue;
317 }
318
319 if (entry->latency < 0) {
320 pr_warn("pm_qos: Latency requirement cannot be negative: %d\n",
321 entry->latency);
322 kfree(entry);
323 continue;
324 }
325
326 list_add_tail(&entry->node, &pm_qos_boot_list);
327 }
328
329 free_cpumask_var(covered);
330 return 0;
331
332 cleanup:
333 list_for_each_entry_safe(entry, tentry, &pm_qos_boot_list, node) {
334 list_del(&entry->node);
335 kfree(entry);
336 }
337
338 free_cpumask_var(covered);
> 339 return ret;
340 }
341 early_initcall(init_pm_qos_latency_us_setup);
342
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Aaron,
kernel test robot noticed the following build warnings:
[auto build test WARNING on driver-core/driver-core-testing]
[also build test WARNING on driver-core/driver-core-next driver-core/driver-core-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master amd-pstate/linux-next amd-pstate/bleeding-edge v6.19-rc6 next-20260122]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Aaron-Tomlin/PM-QoS-Introduce-boot-parameter-pm_qos_resume_latency_us/20260123-090409
base: driver-core/driver-core-testing
patch link: https://lore.kernel.org/r/20260123010024.3301276-1-atomlin%40atomlin.com
patch subject: [PATCH] PM: QoS: Introduce boot parameter pm_qos_resume_latency_us
config: s390-allnoconfig (https://download.01.org/0day-ci/archive/20260123/202601231542.GkFyNtdd-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 9b8addffa70cee5b2acc5454712d9cf78ce45710)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260123/202601231542.GkFyNtdd-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601231542.GkFyNtdd-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> kernel/power/qos.c:56:13: warning: unused variable 'pm_qos_resume_latency_cmdline' [-Wunused-variable]
56 | static char pm_qos_resume_latency_cmdline[COMMAND_LINE_SIZE] __initdata;
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
vim +/pm_qos_resume_latency_cmdline +56 kernel/power/qos.c
55
> 56 static char pm_qos_resume_latency_cmdline[COMMAND_LINE_SIZE] __initdata;
57
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Aaron,
kernel test robot noticed the following build warnings:
[auto build test WARNING on driver-core/driver-core-testing]
[also build test WARNING on driver-core/driver-core-next driver-core/driver-core-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master amd-pstate/linux-next amd-pstate/bleeding-edge v6.16-rc1 next-20260122]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Aaron-Tomlin/PM-QoS-Introduce-boot-parameter-pm_qos_resume_latency_us/20260123-090409
base: driver-core/driver-core-testing
patch link: https://lore.kernel.org/r/20260123010024.3301276-1-atomlin%40atomlin.com
patch subject: [PATCH] PM: QoS: Introduce boot parameter pm_qos_resume_latency_us
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260123/202601230729.fH9djzc0-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260123/202601230729.fH9djzc0-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601230729.fH9djzc0-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> kernel/power/qos.c:339:9: warning: variable 'ret' is uninitialized when used here [-Wuninitialized]
339 | return ret;
| ^~~
kernel/power/qos.c:266:9: note: initialize the variable 'ret' to silence this warning
266 | int ret;
| ^
| = 0
1 warning generated.
vim +/ret +339 kernel/power/qos.c
245
246 /* init_pm_qos_latency_us_setup - Parse the pm_qos_latency_us boot parameter.
247 *
248 * Parses the kernel command line option "pm_qos_resume_latency_us=" to establish
249 * per-CPU resume latency constraints. These constraints are applied
250 * immediately when a CPU is registered.
251 *
252 * Syntax: pm_qos_resume_latency_us=<cpu-list>:<value>[,<cpu-list>:<value>...]
253 * Example: pm_qos_resume_latency_us=0-3:0,4-7:20
254 *
255 * The parsing logic enforces a "First Match Wins" policy. If a CPU is
256 * covered by multiple entries in the list, only the first valid entry
257 * applies. Any subsequent overlapping ranges for that CPU are ignored.
258 *
259 * Return: 0 on success, or a negative error code on failure.
260 */
261 static int __init init_pm_qos_latency_us_setup(void)
262 {
263 char *token, *cmd = pm_qos_resume_latency_cmdline;
264 struct pm_qos_boot_entry *entry, *tentry;
265 cpumask_var_t covered;
266 int ret;
267
268 if (boot_option_idle_override == IDLE_POLL) {
269 pr_warn("pm_qos: Cannot be used with idle=poll\n");
270 return -EINVAL;
271 }
272
273 if (!zalloc_cpumask_var(&covered, GFP_KERNEL)) {
274 pr_warn("pm_qos: Failed to allocate memory for parsing boot parameter\n");
275 return -ENOMEM;
276 }
277
278 while ((token = strsep(&cmd, ",")) != NULL) {
279 char *str_range, *str_val;
280
281 str_range = strsep(&token, ":");
282 str_val = token;
283
284 if (!str_val) {
285 pr_warn("pm_qos: Missing value range %s\n",
286 str_range);
287 continue;
288 }
289
290 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
291 if (!entry) {
292 pr_warn("pm_qos: Failed to allocate memory for boot entry\n");
293 goto cleanup;
294 }
295
296 if (cpulist_parse(str_range, &entry->mask)) {
297 pr_warn("pm_qos: Failed to parse cpulist range %s\n",
298 str_range);
299 kfree(entry);
300 continue;
301 }
302
303 cpumask_andnot(&entry->mask, &entry->mask, covered);
304 if (cpumask_empty(&entry->mask)) {
305 pr_warn("pm_qos: Entry %s already covered, ignoring\n",
306 str_range);
307 kfree(entry);
308 continue;
309 }
310 cpumask_or(covered, covered, &entry->mask);
311
312 if (kstrtos32(str_val, 0, &entry->latency)) {
313 pr_warn("pm_qos: Invalid latency requirement value %s\n",
314 str_val);
315 kfree(entry);
316 continue;
317 }
318
319 if (entry->latency < 0) {
320 pr_warn("pm_qos: Latency requirement cannot be negative: %d\n",
321 entry->latency);
322 kfree(entry);
323 continue;
324 }
325
326 list_add_tail(&entry->node, &pm_qos_boot_list);
327 }
328
329 free_cpumask_var(covered);
330 return 0;
331
332 cleanup:
333 list_for_each_entry_safe(entry, tentry, &pm_qos_boot_list, node) {
334 list_del(&entry->node);
335 kfree(entry);
336 }
337
338 free_cpumask_var(covered);
> 339 return ret;
340 }
341 early_initcall(init_pm_qos_latency_us_setup);
342
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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