KVM: arm64: Tidy up kvm_map_vector()

The bulk of the work in kvm_map_vector() is conditional on the
ARM64_HARDEN_EL2_VECTORS capability, so return early if that is not set
and make the code a bit easier to read.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20201113113847.21619-3-will@kernel.org

arch/arm64/kvm/arm.c

@@ -1297,6 +1297,8 @@ static unsigned long nvhe_percpu_order(void)
 
 static int kvm_map_vectors(void)
 {
+	int slot;
+
 	/*
 	 * SV2  = ARM64_SPECTRE_V2
 	 * HEL2 = ARM64_HARDEN_EL2_VECTORS
@@ -1306,22 +1308,20 @@ static int kvm_map_vectors(void)
 	 * !SV2 +  HEL2 -> allocate one vector slot and use exec mapping
 	 *  SV2 +  HEL2 -> use hardened vectors and use exec mapping
 	 */
-	if (cpus_have_const_cap(ARM64_HARDEN_EL2_VECTORS)) {
-		phys_addr_t vect_pa = __pa_symbol(__bp_harden_hyp_vecs);
-		unsigned long size = __BP_HARDEN_HYP_VECS_SZ;
+	if (!cpus_have_const_cap(ARM64_HARDEN_EL2_VECTORS))
+		return 0;
 
-		/*
-		 * Always allocate a spare vector slot, as we don't
-		 * know yet which CPUs have a BP hardening slot that
-		 * we can reuse.
-		 */
-		__kvm_harden_el2_vector_slot = atomic_inc_return(&arm64_el2_vector_last_slot);
-		BUG_ON(__kvm_harden_el2_vector_slot >= BP_HARDEN_EL2_SLOTS);
-		return create_hyp_exec_mappings(vect_pa, size,
-						&__kvm_bp_vect_base);
-	}
+	/*
+	 * Always allocate a spare vector slot, as we don't know yet which CPUs
+	 * have a BP hardening slot that we can reuse.
+	 */
+	slot = atomic_inc_return(&arm64_el2_vector_last_slot);
+	BUG_ON(slot >= BP_HARDEN_EL2_SLOTS);
+	__kvm_harden_el2_vector_slot = slot;
 
-	return 0;
+	return create_hyp_exec_mappings(__pa_symbol(__bp_harden_hyp_vecs),
+					__BP_HARDEN_HYP_VECS_SZ,
+					&__kvm_bp_vect_base);
 }
 
 static void cpu_init_hyp_mode(void)