# hv_vcpu_get_sme_z_reg(_:_:_:_:) Returns the value of a vCPU Z vector register in streaming Scalable Vector Extension (SVE) mode. ``` func hv_vcpu_get_sme_z_reg(_ vcpu: hv_vcpu_t, _ reg: hv_sme_z_reg_t, _ value: UnsafeMutablePointer, _ length: Int) -> hv_return_t ``` ## Parameters `vcpu` The ID of the vCPU instance. `reg` The ID of the Z vector register. `value` A pointer to the register value to set. `length` The length of the Z register value, in bytes. ## Return Value `HV_SUCCESS` on success, an error code otherwise. ## Discussion > Important: > You need to call this on the owning thread. The method returns an error if not in streaming SVE mode, for example if[`streaming_sve_mode_enabled`](/documentation/Hypervisor/hv_vcpu_sme_state_t/streaming_sve_mode_enabled) is `false`, or if the value `length` isn’t maximum SVL bytes. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)