KVM: Move apic timer migration away from critical section

Migrating the apic timer in the critical section is not very nice, and is
absolutely horrible with the real-time port.  Move migration to the regular
vcpu execution path, triggered by a new bitflag.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Avi Kivity <avi@qumranet.com>

4 files changed, 12 insertions, 4 deletions

diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 53c7f48254be..fa5ed5d59b5d 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -83,6 +83,6 @@ void kvm_pic_reset(struct kvm_kpic_state *s);
 void kvm_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
 void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);
 void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu);
-void kvm_migrate_apic_timer(struct kvm_vcpu *vcpu);
+void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu);
 
 #endif
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e7513bb98af1..2cbee9479ce4 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1092,7 +1092,7 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu)
         start_apic_timer(apic);
 }
 
-void kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
+void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
 {
         struct kvm_lapic *apic = vcpu->arch.apic;
         struct hrtimer *timer;
@@ -1104,7 +1104,6 @@ void kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
         if (hrtimer_cancel(timer))
                 hrtimer_start(timer, timer->expires, HRTIMER_MODE_ABS);
 }
-EXPORT_SYMBOL_GPL(kvm_migrate_apic_timer);
 
 void kvm_lapic_sync_from_vapic(struct kvm_vcpu *vcpu)
 {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f0493e7dcf0c..8f94a0b89dff 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2518,13 +2518,16 @@ again:
         if (unlikely(r))
                 goto out;
 
-        if (vcpu->requests)
+        if (vcpu->requests) {
+                if (test_and_clear_bit(KVM_REQ_MIGRATE_TIMER, &vcpu->requests))
+                        __kvm_migrate_apic_timer(vcpu);
                 if (test_and_clear_bit(KVM_REQ_REPORT_TPR_ACCESS,
                                        &vcpu->requests)) {
                         kvm_run->exit_reason = KVM_EXIT_TPR_ACCESS;
                         r = 0;
                         goto out;
                 }
+        }
 
         kvm_inject_pending_timer_irqs(vcpu);
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2714068ee8bc..ea4764b0a2f4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -35,6 +35,7 @@
  * vcpu->requests bit members
  */
 #define KVM_REQ_TLB_FLUSH          0
+#define KVM_REQ_MIGRATE_TIMER      1
 #define KVM_REQ_REPORT_TPR_ACCESS  2
 
 struct kvm_vcpu;
@@ -277,6 +278,11 @@ static inline gpa_t gfn_to_gpa(gfn_t gfn)
         return (gpa_t)gfn << PAGE_SHIFT;
 }
 
+static inline void kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
+{
+        set_bit(KVM_REQ_MIGRATE_TIMER, &vcpu->requests);
+}
+
 enum kvm_stat_kind {
         KVM_STAT_VM,
         KVM_STAT_VCPU,