cpuidle-haltpoll: disable host side polling when kvm virtualized

When performing guest side polling, it is not necessary to
also perform host side polling.

So disable host side polling, via the new MSR interface,
when loading cpuidle-haltpoll driver.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index b7f34fe2171e..f48401be8ce0 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -875,3 +875,45 @@ void __init kvm_spinlock_init(void)
 }
 
 #endif	/* CONFIG_PARAVIRT_SPINLOCKS */
+
+#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL
+
+static void kvm_disable_host_haltpoll(void *i)
+{
+	wrmsrl(MSR_KVM_POLL_CONTROL, 0);
+}
+
+static void kvm_enable_host_haltpoll(void *i)
+{
+	wrmsrl(MSR_KVM_POLL_CONTROL, 1);
+}
+
+void arch_haltpoll_enable(void)
+{
+	if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) {
+		printk(KERN_ERR "kvm: host does not support poll control\n");
+		printk(KERN_ERR "kvm: host upgrade recommended\n");
+		return;
+	}
+
+	preempt_disable();
+	/* Enable guest halt poll disables host halt poll */
+	kvm_disable_host_haltpoll(NULL);
+	smp_call_function(kvm_disable_host_haltpoll, NULL, 1);
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(arch_haltpoll_enable);
+
+void arch_haltpoll_disable(void)
+{
+	if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL))
+		return;
+
+	preempt_disable();
+	/* Enable guest halt poll disables host halt poll */
+	kvm_enable_host_haltpoll(NULL);
+	smp_call_function(kvm_enable_host_haltpoll, NULL, 1);
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(arch_haltpoll_disable);
+#endif