cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available

The downside of guest side polling is that polling is performed even
with other runnable tasks in the host. However, even if poll in kvm
can aware whether or not other runnable tasks in the same pCPU, it
can still incur extra overhead in over-subscribe scenario. Now we can
just enable guest polling when dedicated pCPUs are available.

Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 60bab4a..3726ba4 100644 (file)
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -711,6 +711,7 @@ unsigned int kvm_arch_para_hints(void)
 {
        return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES);
 }
+EXPORT_SYMBOL_GPL(kvm_arch_para_hints);
 
 static uint32_t __init kvm_detect(void)
 {

diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
index 49a65c6..932390b 100644 (file)
--- a/drivers/cpuidle/cpuidle-haltpoll.c
+++ b/drivers/cpuidle/cpuidle-haltpoll.c
@@ -97,7 +97,8 @@ static int __init haltpoll_init(void)
 
        cpuidle_poll_state_init(drv);
 
-       if (!kvm_para_available())
+       if (!kvm_para_available() ||
+               !kvm_para_has_hint(KVM_HINTS_REALTIME))
                return -ENODEV;
 
        ret = cpuidle_register_driver(drv);