KVM: ppc: Handle guest idle by emulating MSR[WE] writes

This reduces host CPU usage when the guest is idle. However, the guest must
set MSR[WE] in its idle loop, which Linux did not do until 2.6.26.

Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
Signed-off-by: Jerone Young <jyoung5@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

2 files changed, 18 insertions, 3 deletions

diff --git a/arch/powerpc/kvm/booke_guest.c b/arch/powerpc/kvm/booke_guest.c
index 6d9884a6884..b3db6f4576a 100644
--- a/arch/powerpc/kvm/booke_guest.c
+++ b/arch/powerpc/kvm/booke_guest.c
@@ -49,6 +49,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "inst_emu",   VCPU_STAT(emulated_inst_exits) },
         { "dec",        VCPU_STAT(dec_exits) },
         { "ext_intr",   VCPU_STAT(ext_intr_exits) },
+        { "halt_wakeup", VCPU_STAT(halt_wakeup) },
         { NULL }
 };
 
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index bad40bd2d3a..777e0f34e0e 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -36,13 +36,12 @@ gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn)
 
 int kvm_cpu_has_interrupt(struct kvm_vcpu *v)
 {
-        /* XXX implement me */
-        return 0;
+        return !!(v->arch.pending_exceptions);
 }
 
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
 {
-        return 1;
+        return !(v->arch.msr & MSR_WE);
 }
 
 
@@ -214,6 +213,11 @@ static void kvmppc_decrementer_func(unsigned long data)
         struct kvm_vcpu *vcpu = (struct kvm_vcpu *)data;
 
         kvmppc_queue_exception(vcpu, BOOKE_INTERRUPT_DECREMENTER);
+
+        if (waitqueue_active(&vcpu->wq)) {
+                wake_up_interruptible(&vcpu->wq);
+                vcpu->stat.halt_wakeup++;
+        }
 }
 
 int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
@@ -339,6 +343,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
         int r;
         sigset_t sigsaved;
 
+        vcpu_load(vcpu);
+
         if (vcpu->sigset_active)
                 sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);
 
@@ -363,12 +369,20 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
         if (vcpu->sigset_active)
                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 
+        vcpu_put(vcpu);
+
         return r;
 }
 
 int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, struct kvm_interrupt *irq)
 {
         kvmppc_queue_exception(vcpu, BOOKE_INTERRUPT_EXTERNAL);
+
+        if (waitqueue_active(&vcpu->wq)) {
+                wake_up_interruptible(&vcpu->wq);
+                vcpu->stat.halt_wakeup++;
+        }
+
         return 0;
 }