Bug 922923

It looks like this configuration is passing the test for pstate registers having non-zero values which is where the x86_64 build was falling over.  From inspection it looks like the MPERF MSR is not advancing.  Could you try the following patch it checks for all the MSRs tht the driver uses have something rational in them.



commit 866111646f2c5d4c6c25e2bb97f5c61c3992defb
Author: Dirk Brandewie <dirk.brandewie>
Date:   Mon Mar 18 16:55:02 2013 -0700

    cpufreq/intel_pstate: Add function to check that all MSR's 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.
    
    Signed-off-by: Dirk Brandewie <dirk.brandewie>
---
 drivers/cpufreq/intel_pstate.c |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index f6dd1e7..cd9c5f4 100644
--- 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());

(In reply to comment #1)
> It looks like this configuration is passing the test for pstate registers
> having non-zero values which is where the x86_64 build was falling over. 
> From inspection it looks like the MPERF MSR is not advancing.  Could you try
> the following patch it checks for all the MSRs tht the driver uses have
> something rational in them.

Works for me - i686 SB now boots without activating the pstate driver.  Actually, x86_64 SB also skips the pstate driver now, so the fact that it activated before may have been more of a fluke.  I suppose it makes sense that this stuff isn't really needed for vcpus, as the host will deal with it.

applied in kernel-3.9.0-0.rc3.git0.4.fc19