KVM: PPC: Book3S PR: Add guard code to prevent returning to guest with PR=0 and Transactional state

Currently PR KVM doesn't support transaction memory in guest privileged
state.

This patch adds a check at setting guest msr, so that we can never return
to guest with PR=0 and TS=0b10. A tabort will be emulated to indicate
this and fail transaction immediately.

[paulus@ozlabs.org - don't change the TM_CAUSE_MISC definition, instead
 use TM_CAUSE_KVM_FAC_UNAV.]

Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index 34f910e..67d0fb40 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -199,7 +199,7 @@ static void kvmppc_emulate_trchkpt(struct kvm_vcpu *vcpu)
 }
 
 /* emulate tabort. at guest privilege state */
-static void kvmppc_emulate_tabort(struct kvm_vcpu *vcpu, int ra_val)
+void kvmppc_emulate_tabort(struct kvm_vcpu *vcpu, int ra_val)
 {
 	/* currently we only emulate tabort. but no emulation of other
 	 * tabort variants since there is no kernel usage of them at