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>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/asm-powerpc/kvm_ppc.h b/include/asm-powerpc/kvm_ppc.h
index 7ac820308a7e..b35a7e3ef978 100644
--- a/include/asm-powerpc/kvm_ppc.h
+++ b/include/asm-powerpc/kvm_ppc.h
@@ -77,12 +77,17 @@ static inline void kvmppc_clear_exception(struct kvm_vcpu *vcpu, int exception)
         clear_bit(priority, &vcpu->arch.pending_exceptions);
 }
 
+/* Helper function for "full" MSR writes. No need to call this if only EE is
+ * changing. */
 static inline void kvmppc_set_msr(struct kvm_vcpu *vcpu, u32 new_msr)
 {
         if ((new_msr & MSR_PR) != (vcpu->arch.msr & MSR_PR))
                 kvmppc_mmu_priv_switch(vcpu, new_msr & MSR_PR);
 
         vcpu->arch.msr = new_msr;
+
+        if (vcpu->arch.msr & MSR_WE)
+                kvm_vcpu_block(vcpu);
 }
 
 #endif /* __POWERPC_KVM_PPC_H__ */