From: Wanpeng Li <wanpengli@tencent.com>
Subject: cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available
References: jsc#SLE-11312
Patch-Mainline: v5.4-rc1
Git-commit: 1328edca4a142ee3c7442d1eece2c3ca383eff35


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>


Signed-off-by:  <trenn@suse.com>
---
 arch/x86/kernel/kvm.c              |    1 +
 drivers/cpuidle/cpuidle-haltpoll.c |    3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -705,6 +705,7 @@
 {
 	return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES);
 }
+EXPORT_SYMBOL_GPL(kvm_arch_para_hints);
 
 static uint32_t __init kvm_detect(void)
 {
--- a/drivers/cpuidle/cpuidle-haltpoll.c
+++ b/drivers/cpuidle/cpuidle-haltpoll.c
@@ -97,7 +97,8 @@
 
 	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);