From: Wanpeng Li <[email protected]> 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 <[email protected]> Cc: Rafael J. Wysocki <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Radim Krčmář <[email protected]> Signed-off-by: Wanpeng Li <[email protected]> -- v1 -> v2: * export kvm_arch_para_hints to fix haltpoll driver build as module error * just disable haltpoll driver instead of both driver and governor since KVM_HINTS_REALTIME is not defined in other arches, and governor doesn't depend on x86, to fix the warning on powerpc arch/x86/kernel/kvm.c | 1 + drivers/cpuidle/cpuidle-haltpoll.c | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index f48401b..68463c1 100644 --- 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 9ac093d..7aee38a 100644 --- a/drivers/cpuidle/cpuidle-haltpoll.c +++ b/drivers/cpuidle/cpuidle-haltpoll.c @@ -53,7 +53,8 @@ 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 0; ret = cpuidle_register(&haltpoll_driver, NULL); -- 2.7.4
