cpuidle-haltpoll: vcpu hotplug support

When cpus != maxcpus cpuidle-haltpoll will fail to register all vcpus
past the online ones and thus fail to register the idle driver.
This is because cpuidle_add_sysfs() will return with -ENODEV as a
consequence from get_cpu_device() return no device for a non-existing
CPU.

Instead switch to cpuidle_register_driver() and manually register each
of the present cpus through cpuhp_setup_state() callbacks and future
ones that get onlined or offlined. This mimmics similar logic that
intel_idle does.

Fixes: fa86ee90eb11 ("add cpuidle-haltpoll driver")
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 6 insertions, 12 deletions

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index f48401be8ce0..60bab4a3b36b 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -888,32 +888,26 @@ static void kvm_enable_host_haltpoll(void *i)
 	wrmsrl(MSR_KVM_POLL_CONTROL, 1);
 }
 
-void arch_haltpoll_enable(void)
+void arch_haltpoll_enable(unsigned int cpu)
 {
 	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");
+		pr_err_once("kvm: host does not support poll control\n");
+		pr_err_once("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();
+	smp_call_function_single(cpu, kvm_disable_host_haltpoll, NULL, 1);
 }
 EXPORT_SYMBOL_GPL(arch_haltpoll_enable);
 
-void arch_haltpoll_disable(void)
+void arch_haltpoll_disable(unsigned int cpu)
 {
 	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();
+	smp_call_function_single(cpu, kvm_enable_host_haltpoll, NULL, 1);
 }
 EXPORT_SYMBOL_GPL(arch_haltpoll_disable);
 #endif