KVM: PPC: Book3S HV P9: Move nested guest entry into its own function

Move the part of the guest entry which is specific to nested HV into its
own function. This is just refactoring.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-31-npiggin@gmail.com

arch/powerpc/kvm/book3s_hv.c

@@ -3822,6 +3822,72 @@ static void vcpu_vpa_increment_dispatch(struct kvm_vcpu *vcpu)
 	}
 }
 
+/* call our hypervisor to load up HV regs and go */
+static int kvmhv_vcpu_entry_p9_nested(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpcr, u64 *tb)
+{
+	struct kvmppc_vcore *vc = vcpu->arch.vcore;
+	unsigned long host_psscr;
+	struct hv_guest_state hvregs;
+	int trap;
+	s64 dec;
+
+	/*
+	 * We need to save and restore the guest visible part of the
+	 * psscr (i.e. using SPRN_PSSCR_PR) since the hypervisor
+	 * doesn't do this for us. Note only required if pseries since
+	 * this is done in kvmhv_vcpu_entry_p9() below otherwise.
+	 */
+	host_psscr = mfspr(SPRN_PSSCR_PR);
+	mtspr(SPRN_PSSCR_PR, vcpu->arch.psscr);
+	kvmhv_save_hv_regs(vcpu, &hvregs);
+	hvregs.lpcr = lpcr;
+	vcpu->arch.regs.msr = vcpu->arch.shregs.msr;
+	hvregs.version = HV_GUEST_STATE_VERSION;
+	if (vcpu->arch.nested) {
+		hvregs.lpid = vcpu->arch.nested->shadow_lpid;
+		hvregs.vcpu_token = vcpu->arch.nested_vcpu_id;
+	} else {
+		hvregs.lpid = vcpu->kvm->arch.lpid;
+		hvregs.vcpu_token = vcpu->vcpu_id;
+	}
+	hvregs.hdec_expiry = time_limit;
+
+	/*
+	 * When setting DEC, we must always deal with irq_work_raise
+	 * via NMI vs setting DEC. The problem occurs right as we
+	 * switch into guest mode if a NMI hits and sets pending work
+	 * and sets DEC, then that will apply to the guest and not
+	 * bring us back to the host.
+	 *
+	 * irq_work_raise could check a flag (or possibly LPCR[HDICE]
+	 * for example) and set HDEC to 1? That wouldn't solve the
+	 * nested hv case which needs to abort the hcall or zero the
+	 * time limit.
+	 *
+	 * XXX: Another day's problem.
+	 */
+	mtspr(SPRN_DEC, kvmppc_dec_expires_host_tb(vcpu) - *tb);
+
+	mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
+	mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
+	trap = plpar_hcall_norets(H_ENTER_NESTED, __pa(&hvregs),
+				  __pa(&vcpu->arch.regs));
+	kvmhv_restore_hv_return_state(vcpu, &hvregs);
+	vcpu->arch.shregs.msr = vcpu->arch.regs.msr;
+	vcpu->arch.shregs.dar = mfspr(SPRN_DAR);
+	vcpu->arch.shregs.dsisr = mfspr(SPRN_DSISR);
+	vcpu->arch.psscr = mfspr(SPRN_PSSCR_PR);
+	mtspr(SPRN_PSSCR_PR, host_psscr);
+
+	dec = mfspr(SPRN_DEC);
+	if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */
+		dec = (s32) dec;
+	*tb = mftb();
+	vcpu->arch.dec_expires = dec + (*tb + vc->tb_offset);
+
+	return trap;
+}
+
 /*
  * Guest entry for POWER9 and later CPUs.
  */
@@ -3830,7 +3896,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
 {
 	struct kvmppc_vcore *vc = vcpu->arch.vcore;
 	struct p9_host_os_sprs host_os_sprs;
-	s64 dec;
 	u64 next_timer;
 	unsigned long msr;
 	int trap;
@@ -3883,63 +3948,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
 	switch_pmu_to_guest(vcpu, &host_os_sprs);
 
 	if (kvmhv_on_pseries()) {
-		/*
-		 * We need to save and restore the guest visible part of the
-		 * psscr (i.e. using SPRN_PSSCR_PR) since the hypervisor
-		 * doesn't do this for us. Note only required if pseries since
-		 * this is done in kvmhv_vcpu_entry_p9() below otherwise.
-		 */
-		unsigned long host_psscr;
-		/* call our hypervisor to load up HV regs and go */
-		struct hv_guest_state hvregs;
-
-		host_psscr = mfspr(SPRN_PSSCR_PR);
-		mtspr(SPRN_PSSCR_PR, vcpu->arch.psscr);
-		kvmhv_save_hv_regs(vcpu, &hvregs);
-		hvregs.lpcr = lpcr;
-		vcpu->arch.regs.msr = vcpu->arch.shregs.msr;
-		hvregs.version = HV_GUEST_STATE_VERSION;
-		if (vcpu->arch.nested) {
-			hvregs.lpid = vcpu->arch.nested->shadow_lpid;
-			hvregs.vcpu_token = vcpu->arch.nested_vcpu_id;
-		} else {
-			hvregs.lpid = vcpu->kvm->arch.lpid;
-			hvregs.vcpu_token = vcpu->vcpu_id;
-		}
-		hvregs.hdec_expiry = time_limit;
-
-		/*
-		 * When setting DEC, we must always deal with irq_work_raise
-		 * via NMI vs setting DEC. The problem occurs right as we
-		 * switch into guest mode if a NMI hits and sets pending work
-		 * and sets DEC, then that will apply to the guest and not
-		 * bring us back to the host.
-		 *
-		 * irq_work_raise could check a flag (or possibly LPCR[HDICE]
-		 * for example) and set HDEC to 1? That wouldn't solve the
-		 * nested hv case which needs to abort the hcall or zero the
-		 * time limit.
-		 *
-		 * XXX: Another day's problem.
-		 */
-		mtspr(SPRN_DEC, kvmppc_dec_expires_host_tb(vcpu) - *tb);
-
-		mtspr(SPRN_DAR, vcpu->arch.shregs.dar);
-		mtspr(SPRN_DSISR, vcpu->arch.shregs.dsisr);
-		trap = plpar_hcall_norets(H_ENTER_NESTED, __pa(&hvregs),
-					  __pa(&vcpu->arch.regs));
-		kvmhv_restore_hv_return_state(vcpu, &hvregs);
-		vcpu->arch.shregs.msr = vcpu->arch.regs.msr;
-		vcpu->arch.shregs.dar = mfspr(SPRN_DAR);
-		vcpu->arch.shregs.dsisr = mfspr(SPRN_DSISR);
-		vcpu->arch.psscr = mfspr(SPRN_PSSCR_PR);
-		mtspr(SPRN_PSSCR_PR, host_psscr);
-
-		dec = mfspr(SPRN_DEC);
-		if (!(lpcr & LPCR_LD)) /* Sign extend if not using large decrementer */
-			dec = (s32) dec;
-		*tb = mftb();
-		vcpu->arch.dec_expires = dec + (*tb + vc->tb_offset);
+		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 &&