KVM: arm64: Hoist SVE check into KVM_ARM_VCPU_INIT ioctl handler

Test that the system supports SVE before ever getting to
kvm_reset_vcpu().

Link: https://lore.kernel.org/r/20230920195036.1169791-4-oliver.upton@linux.devSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/kvm/arm.c

@@ -1200,6 +1200,9 @@ static unsigned long system_supported_vcpu_features(void)
 	if (!kvm_arm_support_pmu_v3())
 		clear_bit(KVM_ARM_VCPU_PMU_V3, &features);
 
+	if (!system_supports_sve())
+		clear_bit(KVM_ARM_VCPU_SVE, &features);
+
 	return features;
 }
 

arch/arm64/kvm/reset.c

@@ -73,11 +73,8 @@ int __init kvm_arm_init_sve(void)
 	return 0;
 }
 
-static int kvm_vcpu_enable_sve(struct kvm_vcpu *vcpu)
+static void kvm_vcpu_enable_sve(struct kvm_vcpu *vcpu)
 {
-	if (!system_supports_sve())
-		return -EINVAL;
-
 	vcpu->arch.sve_max_vl = kvm_sve_max_vl;
 
 	/*
@@ -86,8 +83,6 @@ static int kvm_vcpu_enable_sve(struct kvm_vcpu *vcpu)
 	 * kvm_arm_vcpu_finalize(), which freezes the configuration.
 	 */
 	vcpu_set_flag(vcpu, GUEST_HAS_SVE);
-
-	return 0;
 }
 
 /*
@@ -231,11 +226,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 	}
 
 	if (!kvm_arm_vcpu_sve_finalized(vcpu)) {
-		if (test_bit(KVM_ARM_VCPU_SVE, vcpu->arch.features)) {
-			ret = kvm_vcpu_enable_sve(vcpu);
-			if (ret)
-				goto out;
-		}
+		if (test_bit(KVM_ARM_VCPU_SVE, vcpu->arch.features))
+			kvm_vcpu_enable_sve(vcpu);
 	} else {
 		kvm_vcpu_reset_sve(vcpu);
 	}