[PATCH v5 7/9] x86/intel_pstate: add a booting param to select the driver to load

[Wei Wang <wei.w.wang@intel.com>]

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.

Also, adding the intel_pstate booting parameter to
xen-command-line.markdown.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
---
 docs/misc/xen-command-line.markdown      | 7 +++++++
 xen/arch/x86/acpi/cpufreq/cpufreq.c      | 9 ++++++---
 xen/arch/x86/acpi/cpufreq/intel_pstate.c | 4 ++++
 3 files changed, 17 insertions(+), 3 deletions(-)

 changes in v5:
 1) move the booting parameter into the intel_pstate_init() function - have
    it be a local variable;
 2) rename "intel_pstate_load" to "load".

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index a2e427c..2d70137 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -849,6 +849,13 @@ debug hypervisor only).
 ### idle\_latency\_factor
 > `= <integer>`
 
+### intel\_pstate
+> `= <boolean>`
+
+> Default: `false`
+
+Enable the loading of the intel pstate driver.
+
 ### ioapic\_ack
 > `= old | new`
 
diff --git a/xen/arch/x86/acpi/cpufreq/cpufreq.c b/xen/arch/x86/acpi/cpufreq/cpufreq.c
index 8494fa0..7e517b9 100644
--- a/xen/arch/x86/acpi/cpufreq/cpufreq.c
+++ b/xen/arch/x86/acpi/cpufreq/cpufreq.c
@@ -40,6 +40,7 @@
 #include <asm/processor.h>
 #include <asm/percpu.h>
 #include <asm/cpufeature.h>
+#include <asm/cpufreq.h>
 #include <acpi/acpi.h>
 #include <acpi/cpufreq/cpufreq.h>
 
@@ -647,9 +648,11 @@ 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 3292bcd..4ebd9c7 100644
--- a/xen/arch/x86/acpi/cpufreq/intel_pstate.c
+++ b/xen/arch/x86/acpi/cpufreq/intel_pstate.c
@@ -843,7 +843,11 @@ int __init intel_pstate_init(void)
     int cpu, rc = 0;
     const struct x86_cpu_id *id;
     struct cpu_defaults *cpu_info;
+    static bool_t __read_mostly load;
+    boolean_param("intel_pstate", load);
 
+    if ( !load )
+        return -ENODEV;
 
     id = x86_match_cpu(intel_pstate_cpu_ids);
     if ( !id )
-- 
1.9.1