cpufreq / intel_pstate: Add function to check that all MSRs are valid

Some VMs seem to try to implement some MSRs but not all the registers
the driver needs.  Check to make sure all the MSR that we need are
available. If any of the required MSRs are not available refuse to
load.

References: https://bugzilla.redhat.com/show_bug.cgi?id=922923
Reported-by: Josh Stone <jistone@redhat.com>
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index f6dd1e7611293bf5a66531f2acb285713439430c..cd9c5f4f580563a96db8773580be6916771df07f 100644 (file)
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -752,6 +752,29 @@ static struct cpufreq_driver intel_pstate_driver = {
 
 static int __initdata no_load;
 
+static int intel_pstate_msrs_not_valid(void)
+{
+       /* Check that all the msr's we are using are valid. */
+       u64 aperf, mperf, tmp;
+
+       rdmsrl(MSR_IA32_APERF, aperf);
+       rdmsrl(MSR_IA32_MPERF, mperf);
+
+       if (!intel_pstate_min_pstate() ||
+               !intel_pstate_max_pstate() ||
+               !intel_pstate_turbo_pstate())
+               return -ENODEV;
+
+       rdmsrl(MSR_IA32_APERF, tmp);
+       if (!(tmp - aperf))
+               return -ENODEV;
+
+       rdmsrl(MSR_IA32_MPERF, tmp);
+       if (!(tmp - mperf))
+               return -ENODEV;
+
+       return 0;
+}
 static int __init intel_pstate_init(void)
 {
        int cpu, rc = 0;
@@ -764,6 +787,9 @@ static int __init intel_pstate_init(void)
        if (!id)
                return -ENODEV;
 
+       if (intel_pstate_msrs_not_valid())
+               return -ENODEV;
+
        pr_info("Intel P-state driver initializing.\n");
 
        all_cpu_data = vmalloc(sizeof(void *) * num_possible_cpus());