KVM: PPC: Book3S HV P9: Implement TM fastpath for guest entry/exit

If TM is not active, only TM register state needs to be saved and
restored, avoiding several mfmsr/mtmsrd instructions and improving
performance.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

arch/powerpc/kvm/book3s_hv_p9_entry.c

@@ -289,8 +289,15 @@ bool load_vcpu_state(struct kvm_vcpu *vcpu,
 
 	if (cpu_has_feature(CPU_FTR_TM) ||
 	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) {
-		kvmppc_restore_tm_hv(vcpu, vcpu->arch.shregs.msr, true);
-		ret = true;
+		unsigned long guest_msr = vcpu->arch.shregs.msr;
+		if (MSR_TM_ACTIVE(guest_msr)) {
+			kvmppc_restore_tm_hv(vcpu, guest_msr, true);
+			ret = true;
+		} else {
+			mtspr(SPRN_TEXASR, vcpu->arch.texasr);
+			mtspr(SPRN_TFHAR, vcpu->arch.tfhar);
+			mtspr(SPRN_TFIAR, vcpu->arch.tfiar);
+		}
 	}
 
 	load_spr_state(vcpu, host_os_sprs);
@@ -316,8 +323,16 @@ void store_vcpu_state(struct kvm_vcpu *vcpu)
 	vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);
 
 	if (cpu_has_feature(CPU_FTR_TM) ||
-	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST))
-		kvmppc_save_tm_hv(vcpu, vcpu->arch.shregs.msr, true);
+	    cpu_has_feature(CPU_FTR_P9_TM_HV_ASSIST)) {
+		unsigned long guest_msr = vcpu->arch.shregs.msr;
+		if (MSR_TM_ACTIVE(guest_msr)) {
+			kvmppc_save_tm_hv(vcpu, guest_msr, true);
+		} else {
+			vcpu->arch.texasr = mfspr(SPRN_TEXASR);
+			vcpu->arch.tfhar = mfspr(SPRN_TFHAR);
+			vcpu->arch.tfiar = mfspr(SPRN_TFIAR);
+		}
+	}
 }
 EXPORT_SYMBOL_GPL(store_vcpu_state);