[PATCH v8 7/8] xen/cpufreq: bypass governor-related para for amd-cppc-epp

[PATCH v8 7/8] xen/cpufreq: bypass governor-related para for amd-cppc-epp

[Penny Zheng]

HWP and amd-cppc-epp are both governor-less driver, so we introduce
"is_governor_less" flag and cpufreq_is_governorless() to help bypass
governor-related info on dealing with cpufreq para.

Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
---
v3 -> v4:
- Include validation check fix here
---
v4 -> v5:
- validation check has beem moved to where XEN_PROCESSOR_PM_CPPC and
XEN_CPPC_INIT have been firstly introduced
- adding "cpufreq_driver.setpolicy == NULL" check to exclude governor-related
para for amd-cppc-epp driver in get/set_cpufreq_para()
---
v5 -> v6:
- add helper cpufreq_is_governorless() to tell whether cpufreq driver is
governor-less
---
v6 -> v7:
- change "hw_auto" to "is_goverless"
- complement comment
- wrap around with PM_OP to avoid violating Misra rule 2.1
---
v7 -> v8:
- change "is_goverless" to "is_governor_less"
- make cpufreq_is_governorless() inline function
---
 tools/misc/xenpm.c                 | 10 +++++++---
 xen/drivers/acpi/pm-op.c           |  4 ++--
 xen/include/acpi/cpufreq/cpufreq.h | 12 ++++++++++++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/tools/misc/xenpm.c b/tools/misc/xenpm.c
index e83dd0d80c..893a0afe11 100644
--- a/tools/misc/xenpm.c
+++ b/tools/misc/xenpm.c
@@ -832,9 +832,13 @@ static void print_cppc_para(unsigned int cpuid,
 /* print out parameters about cpu frequency */
 static void print_cpufreq_para(int cpuid, struct xc_get_cpufreq_para *p_cpufreq)
 {
-    bool hwp = strcmp(p_cpufreq->scaling_driver, XEN_HWP_DRIVER_NAME) == 0;
+    bool is_governor_less = false;
     int i;
 
+    if ( !strcmp(p_cpufreq->scaling_driver, XEN_HWP_DRIVER_NAME) ||
+         !strcmp(p_cpufreq->scaling_driver, XEN_AMD_CPPC_EPP_DRIVER_NAME) )
+        is_governor_less = true;
+
     printf("cpu id               : %d\n", cpuid);
 
     printf("affected_cpus        :");
@@ -842,7 +846,7 @@ static void print_cpufreq_para(int cpuid, struct xc_get_cpufreq_para *p_cpufreq)
         printf(" %d", p_cpufreq->affected_cpus[i]);
     printf("\n");
 
-    if ( hwp )
+    if ( is_governor_less )
         printf("cpuinfo frequency    : base [%"PRIu32"] max [%"PRIu32"]\n",
                p_cpufreq->cpuinfo_min_freq,
                p_cpufreq->cpuinfo_max_freq);
@@ -854,7 +858,7 @@ static void print_cpufreq_para(int cpuid, struct xc_get_cpufreq_para *p_cpufreq)
 
     printf("scaling_driver       : %s\n", p_cpufreq->scaling_driver);
 
-    if ( !hwp )
+    if ( !is_governor_less )
     {
         if ( p_cpufreq->gov_num )
             printf("scaling_avail_gov    : %s\n",
diff --git a/xen/drivers/acpi/pm-op.c b/xen/drivers/acpi/pm-op.c
index 19aedf6b0b..371deaf678 100644
--- a/xen/drivers/acpi/pm-op.c
+++ b/xen/drivers/acpi/pm-op.c
@@ -154,7 +154,7 @@ static int get_cpufreq_para(struct xen_sysctl_pm_op *op)
     else
         strlcpy(op->u.get_para.scaling_driver, "Unknown", CPUFREQ_NAME_LEN);
 
-    if ( !hwp_active() )
+    if ( !cpufreq_is_governorless(op->cpuid) )
     {
         if ( !(scaling_available_governors =
                xzalloc_array(char, gov_num * CPUFREQ_NAME_LEN)) )
@@ -240,7 +240,7 @@ static int set_cpufreq_para(struct xen_sysctl_pm_op *op)
     if ( !policy || !policy->governor )
         return -EINVAL;
 
-    if ( hwp_active() )
+    if ( cpufreq_is_governorless(op->cpuid) )
         return -EOPNOTSUPP;
 
     switch( op->u.set_para.ctrl_type )
diff --git a/xen/include/acpi/cpufreq/cpufreq.h b/xen/include/acpi/cpufreq/cpufreq.h
index 9ef7c4683a..7caeae26cf 100644
--- a/xen/include/acpi/cpufreq/cpufreq.h
+++ b/xen/include/acpi/cpufreq/cpufreq.h
@@ -294,4 +294,16 @@ int acpi_cpufreq_register(void);
 int amd_cppc_cmdline_parse(const char *s, const char *e);
 int amd_cppc_register_driver(void);
 
+/*
+ * Governor-less cpufreq driver indicates the driver doesn't rely on Xen
+ * governor to do performance tuning, mostly it has hardware built-in
+ * algorithm to calculate runtime workload and adjust cores frequency
+ * automatically, like Intel HWP, or CPPC in AMD.
+ */
+static inline bool cpufreq_is_governorless(unsigned int cpuid)
+{
+    return processor_pminfo[cpuid]->init && (hwp_active() ||
+                                             cpufreq_driver.setpolicy);
+}
+
 #endif /* __XEN_CPUFREQ_PM_H__ */
-- 
2.34.1

Re: [PATCH v8 7/8] xen/cpufreq: bypass governor-related para for amd-cppc-epp

[Jan Beulich]

On 28.08.2025 12:05, Penny Zheng wrote:
> HWP and amd-cppc-epp are both governor-less driver, so we introduce
> "is_governor_less" flag and cpufreq_is_governorless() to help bypass
> governor-related info on dealing with cpufreq para.
> 
> Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>

Acked-by: Jan Beulich <jbeulich@suse.com>

Re: [PATCH v8 7/8] xen/cpufreq: bypass governor-related para for amd-cppc-epp

[Anthony PERARD]

On Thu, Aug 28, 2025 at 06:05:34PM +0800, Penny Zheng wrote:
> HWP and amd-cppc-epp are both governor-less driver, so we introduce
> "is_governor_less" flag and cpufreq_is_governorless() to help bypass
> governor-related info on dealing with cpufreq para.
> 
> Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>

Acked-by: Anthony PERARD <anthony.perard@vates.tech>

Thanks,

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