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@intel.com>.

Signed-off-by: Len Brown <len.brown@intel.com>
Do the MSR writes on all CPUs rather than just the current one.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/cpu/mwait-idle.c b/xen/arch/x86/cpu/mwait-idle.c
index c2c8889a697d617bbd58c72bc7512be24c99d7d9..a4a779ba535c91bd6a5e1963d2887707406e1dc2 100644 (file)
--- 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;
 };
 
@@ -537,6 +538,12 @@ static void auto_demotion_disable(void *dummy)
        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;
@@ -569,6 +576,7 @@ static const struct idle_cpu idle_cpu_snb = {
 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 = {
@@ -767,6 +775,9 @@ static int mwait_idle_cpu_init(struct notifier_block *nfb,
        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);
 

diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index 2056501f8705ee6efcf79e6fd41479124d651de2..542222e07ac2a5e7244e0a429eda8464a1f3aa95 100644 (file)
--- 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 */