KVM: PPC: Book3S HV P9: Split !nested case out from guest entry

The differences between nested and !nested will become larger in
later changes so split them out for readability.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220303053315.1056880-5-npiggin@gmail.com

arch/powerpc/kvm/book3s_hv.c

@@ -4029,6 +4029,8 @@ static int kvmhv_vcpu_entry_p9_nested(struct kvm_vcpu *vcpu, u64 time_limit, uns
 static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
 			 unsigned long lpcr, u64 *tb)
 {
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_nested_guest *nested = vcpu->arch.nested;
 	u64 next_timer;
 	int trap;
 
@@ -4048,23 +4050,30 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
 		trap = kvmhv_vcpu_entry_p9_nested(vcpu, time_limit, lpcr, tb);
 
 		/* H_CEDE has to be handled now, not later */
-		if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
+		if (trap == BOOK3S_INTERRUPT_SYSCALL && !nested &&
 		    kvmppc_get_gpr(vcpu, 3) == H_CEDE) {
 			kvmppc_cede(vcpu);
 			kvmppc_set_gpr(vcpu, 3, 0);
 			trap = 0;
 		}
 
-	} else {
-		struct kvm *kvm = vcpu->kvm;
+	} else if (nested) {
+		kvmppc_xive_push_vcpu(vcpu);
+
+		__this_cpu_write(cpu_in_guest, kvm);
+		trap = kvmhv_vcpu_entry_p9(vcpu, time_limit, lpcr, tb);
+		__this_cpu_write(cpu_in_guest, NULL);
 
+		kvmppc_xive_pull_vcpu(vcpu);
+
+	} else {
 		kvmppc_xive_push_vcpu(vcpu);
 
 		__this_cpu_write(cpu_in_guest, kvm);
 		trap = kvmhv_vcpu_entry_p9(vcpu, time_limit, lpcr, tb);
 		__this_cpu_write(cpu_in_guest, NULL);
 
-		if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
+		if (trap == BOOK3S_INTERRUPT_SYSCALL &&
 		    !(vcpu->arch.shregs.msr & MSR_PR)) {
 			unsigned long req = kvmppc_get_gpr(vcpu, 3);