KVM: PPC: Book3S PR: Restore NV regs after emulating mfspr from TM SPRs

Currently kvmppc_handle_fac() will not update NV GPRs and thus it can
return with GUEST_RESUME.

However PR KVM guest always disables MSR_TM bit in privileged state.
If PR privileged-state guest is trying to read TM SPRs, it will
trigger TM facility unavailable exception and fall into
kvmppc_handle_fac().  Then the emulation will be done by
kvmppc_core_emulate_mfspr_pr().  The mfspr instruction can include a
RT with NV reg. So it is necessary to restore NV GPRs at this case, to
reflect the update to NV RT.

This patch make kvmppc_handle_fac() return GUEST_RESUME_NV for TM
facility unavailable exceptions in guest privileged state.
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Reviewed-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_pr.c

@@ -989,6 +989,18 @@ static int kvmppc_handle_fac(struct kvm_vcpu *vcpu, ulong fac)
 		break;
 	}
 
+#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
+	/* Since we disabled MSR_TM at privilege state, the mfspr instruction
+	 * for TM spr can trigger TM fac unavailable. In this case, the
+	 * emulation is handled by kvmppc_emulate_fac(), which invokes
+	 * kvmppc_emulate_mfspr() finally. But note the mfspr can include
+	 * RT for NV registers. So it need to restore those NV reg to reflect
+	 * the update.
+	 */
+	if ((fac == FSCR_TM_LG) && !(kvmppc_get_msr(vcpu) & MSR_PR))
+		return RESUME_GUEST_NV;
+#endif
+
 	return RESUME_GUEST;
 }
 
@@ -1350,8 +1362,7 @@ int kvmppc_handle_exit_pr(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	}
 #ifdef CONFIG_PPC_BOOK3S_64
 	case BOOK3S_INTERRUPT_FAC_UNAVAIL:
-		kvmppc_handle_fac(vcpu, vcpu->arch.shadow_fscr >> 56);
-		r = RESUME_GUEST;
+		r = kvmppc_handle_fac(vcpu, vcpu->arch.shadow_fscr >> 56);
 		break;
 #endif
 	case BOOK3S_INTERRUPT_MACHINE_CHECK: