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# hv_vmx_vcpu_write_vmcs(_:_:_:)

Sets the value of a virtual machine control structure (VMCS) field of a vCPU.

```
func hv_vmx_vcpu_write_vmcs(_ vcpu: hv_vcpuid_t, _ field: UInt32, _ value: UInt64) -> hv_return_t
```

## Parameters

`vcpu`

The ID of the vCPU.

`field`

The ID of the VMCS field. For a list of possible values, see `Virtual Machine Control Structure (VMCS) Field IDs`.

`value`

The new value for `field` in the VMCS.

## Return Value

[`HV_SUCCESS`](/documentation/Hypervisor/HV_SUCCESS) if the operation was successful, otherwise an error code specified in [`hv_return_t`](/documentation/Hypervisor/hv_return_t).

## Discussion

> Important:
> This function must be called by the owning thread.

---

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