KVM: PPC: Book3S HV: Fix mask size for emulated msgsndp

According to ISAv3.1 and ISAv3.0b, the msgsndp is described to split
RB in:
  msgtype <- (RB) 32:36
  payload <- (RB) 37:63
  t       <- (RB) 57:63

The current way of getting 'msgtype', and 't' is missing their MSB:
  msgtype: ((arg >> 27) & 0xf) : Gets (RB) 33:36, missing bit 32
  t:       (arg &= 0x3f)       : Gets (RB) 58:63, missing bit 57

Fixes this by applying the correct mask.

Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201208215707.31149-1-leobras.c@gmail.com

arch/powerpc/kvm/book3s_hv.c

@@ -1241,9 +1241,9 @@ static int kvmppc_emulate_doorbell_instr(struct kvm_vcpu *vcpu)
 	switch (get_xop(inst)) {
 	case OP_31_XOP_MSGSNDP:
 		arg = kvmppc_get_gpr(vcpu, rb);
-		if (((arg >> 27) & 0xf) != PPC_DBELL_SERVER)
+		if (((arg >> 27) & 0x1f) != PPC_DBELL_SERVER)
 			break;
-		arg &= 0x3f;
+		arg &= 0x7f;
 		if (arg >= kvm->arch.emul_smt_mode)
 			break;
 		tvcpu = kvmppc_find_vcpu(kvm, vcpu->vcpu_id - thr + arg);
@@ -1256,7 +1256,7 @@ static int kvmppc_emulate_doorbell_instr(struct kvm_vcpu *vcpu)
 		break;
 	case OP_31_XOP_MSGCLRP:
 		arg = kvmppc_get_gpr(vcpu, rb);
-		if (((arg >> 27) & 0xf) != PPC_DBELL_SERVER)
+		if (((arg >> 27) & 0x1f) != PPC_DBELL_SERVER)
 			break;
 		vcpu->arch.vcore->dpdes = 0;
 		vcpu->arch.doorbell_request = 0;