[Xen-devel] [PATCH v3 08/11] x86/intel_pstate: add a booting param to select the driver to load

[Wei Wang <wei.w.wang@xxxxxxxxx>]

By default, the old P-state driver (acpi-freq) is used. Adding
"intel_pstate" to the Xen booting param list to enable the
use of intel_pstate. However, if intel_pstate is enabled on a
machine which does not support the driver (e.g. Nehalem), the
old P-state driver will be loaded due to the failure loading of
intel_pstate.

Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
---
 xen/arch/x86/acpi/cpufreq/cpufreq.c      | 8 +++++---
 xen/arch/x86/acpi/cpufreq/intel_pstate.c | 6 ++++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/acpi/cpufreq/cpufreq.c 
b/xen/arch/x86/acpi/cpufreq/cpufreq.c
index fa3678d..3765fc4 100644
--- a/xen/arch/x86/acpi/cpufreq/cpufreq.c
+++ b/xen/arch/x86/acpi/cpufreq/cpufreq.c
@@ -650,9 +650,11 @@ static int __init cpufreq_driver_init(void)
     int ret = 0;
 
     if ((cpufreq_controller == FREQCTL_xen) &&
-        (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL))
-        ret = cpufreq_register_driver(&acpi_cpufreq_driver);
-    else if ((cpufreq_controller == FREQCTL_xen) &&
+        (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)) {
+            ret = intel_pstate_init();
+            if (ret)
+                ret = cpufreq_register_driver(&acpi_cpufreq_driver);
+    } else if ((cpufreq_controller == FREQCTL_xen) &&
         (boot_cpu_data.x86_vendor == X86_VENDOR_AMD))
         ret = powernow_register_driver();
 
diff --git a/xen/arch/x86/acpi/cpufreq/intel_pstate.c 
b/xen/arch/x86/acpi/cpufreq/intel_pstate.c
index 48bbc30..d1a6056 100644
--- a/xen/arch/x86/acpi/cpufreq/intel_pstate.c
+++ b/xen/arch/x86/acpi/cpufreq/intel_pstate.c
@@ -749,6 +749,9 @@ static struct cpufreq_driver intel_pstate_driver = {
     .name         = "intel_pstate",
 };
 
+static bool_t __initdata load_intel_pstate;
+boolean_param("intel_pstate", load_intel_pstate);
+
 static int intel_pstate_msrs_not_valid(void)
 {
     if (!pstate_funcs.get_max() ||
@@ -785,6 +788,9 @@ int __init intel_pstate_init(void)
     const struct x86_cpu_id *id;
     struct cpu_defaults *cpu_info;
 
+    if (!load_intel_pstate)
+         return -ENODEV;
+
     id = x86_match_cpu(intel_pstate_cpu_ids);
     if (!id)
         return -ENODEV;
-- 
1.9.1


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