[PATCH 5/7] intel_idle: Add a way to skip the mwait check on all states

[arjan@linux.intel.com]

From: Arjan van de Ven <arjan.van.de.ven@intel.com>

Currently, intel_idle verifies that the cpuid instruction enumerates
that the mwait value for a state is actually supported by the CPU.

Going forward, when running in a VM guest, that check will not work
and we're going to need a way to turn it off.

Add a global bool for this, and uses this in the check
function to short circuit this cpuid check.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
 drivers/idle/intel_idle.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 66d262fd267e..55c3e6ece3dd 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -69,6 +69,7 @@ static int max_cstate = CPUIDLE_STATE_MAX - 1;
 static unsigned int disabled_states_mask __read_mostly;
 static unsigned int preferred_states_mask __read_mostly;
 static bool force_irq_on __read_mostly;
+static bool skip_mwait_check __read_mostly;
 
 static struct cpuidle_device __percpu *intel_idle_cpuidle_devices;
 
@@ -1866,6 +1867,9 @@ static bool __init intel_idle_verify_cstate(unsigned int mwait_hint)
 	unsigned int num_substates = (mwait_substates >> mwait_cstate * 4) &
 					MWAIT_SUBSTATE_MASK;
 
+	if (skip_mwait_check)
+		return true;
+
 	/* Ignore the C-state if there are NO sub-states in CPUID for it. */
 	if (num_substates == 0)
 		return false;
-- 
2.40.1