x86/mwait-idle: disable Baytrail Core and Module C6 auto-demotion

Power efficiency improves on Baytrail (Intel Atom Processor E3000)
when Linux disables C6 auto-demotion.

Based on work by Srinidhi Kasagar <srinidhi.kasagar@xxxxxxxxx>.

Signed-off-by: Len Brown <len.brown@xxxxxxxxx>

Do the MSR writes on all CPUs rather than just the current one.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -483,4 +483,7 @@
 #define _MSR_MISC_FEATURES_CPUID_FAULTING	0
 #define MSR_MISC_FEATURES_CPUID_FAULTING	(1ULL << _MSR_MISC_FEATURES_CPUID_FAULTING)
 
+#define MSR_CC6_DEMOTION_POLICY_CONFIG	0x00000668
+#define MSR_MC6_DEMOTION_POLICY_CONFIG	0x00000669
+
 #endif /* __ASM_MSR_INDEX_H */
--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -88,6 +88,7 @@ struct idle_cpu {
 	 * Indicate which enable bits to clear here.
 	 */
 	unsigned long auto_demotion_disable_flags;
+	bool_t byt_auto_demotion_disable_flag;
 	bool_t disable_promotion_to_c1e;
 };
 
@@ -539,6 +540,12 @@ static void auto_demotion_disable(void *
 	wrmsrl(MSR_NHM_SNB_PKG_CST_CFG_CTL, msr_bits);
 }
 
+static void byt_auto_demotion_disable(void *dummy)
+{
+	wrmsrl(MSR_CC6_DEMOTION_POLICY_CONFIG, 0);
+	wrmsrl(MSR_MC6_DEMOTION_POLICY_CONFIG, 0);
+}
+
 static void c1e_promotion_disable(void *dummy)
 {
 	u64 msr_bits;
@@ -571,6 +578,7 @@ static const struct idle_cpu idle_cpu_sn
 static const struct idle_cpu idle_cpu_byt = {
 	.state_table = byt_cstates,
 	.disable_promotion_to_c1e = 1,
+	.byt_auto_demotion_disable_flag = 1,
 };
 
 static const struct idle_cpu idle_cpu_ivb = {
@@ -769,6 +777,9 @@ static int mwait_idle_cpu_init(struct no
 	if (icpu->auto_demotion_disable_flags)
 		on_selected_cpus(cpumask_of(cpu), auto_demotion_disable, NULL, 1);
 
+	if (icpu->byt_auto_demotion_disable_flag)
+		on_selected_cpus(cpumask_of(cpu), byt_auto_demotion_disable, NULL, 1);
+
 	if (icpu->disable_promotion_to_c1e)
 		on_selected_cpus(cpumask_of(cpu), c1e_promotion_disable, NULL, 1);