[xen staging] xen/cpufreq: bypass governor-related para for amd-cppc-epp

[patchbot@xxxxxxx]

commit 494de59f045fea01956cd252ef35a9c25037cabf
Author:     Penny Zheng <Penny.Zheng@xxxxxxx>
AuthorDate: Thu Sep 25 09:21:41 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Sep 25 10:21:31 2025 +0200

    xen/cpufreq: bypass governor-related para for amd-cppc-epp
    
    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@xxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 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 c7f19cea28..682d092479 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 f50acd7088..4cca42c4fc 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..3efa71d442 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 cpu)
+{
+    return processor_pminfo[cpu]->init && (hwp_active() ||
+                                           cpufreq_driver.setpolicy);
+}
+
 #endif /* __XEN_CPUFREQ_PM_H__ */
--
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