main/syscalls/iommu_create.md

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# zx_iommu_create

## Summary

Create a new IOMMU object in the kernel.

## Declaration

```c
#include <zircon/syscalls.h>

zx_status_t zx_iommu_create(zx_handle_t resource,
                            uint32_t type,
                            const void* desc,
                            size_t desc_size,
                            zx_handle_t* out);
```

## Description

`zx_iommu_create()` creates a new object in the kernel representing an IOMMU device.

The value of *type* determines the interpretation of *desc*.  See below for
details about the values of *type*.

Upon success, a handle for the new IOMMU is returned.  This handle will have rights
`ZX_RIGHT_DUPLICATE` and `ZX_RIGHT_TRANSFER`.

### *type* = `ZX_IOMMU_TYPE_STUB`

This type represents a no-op IOMMU.  It provides no hardware-level protections
against unauthorized access to memory.  It does allow pinning of physical memory
pages, to prevent the reuse of a page until the driver using the page says it is
done with it.

*desc* must be a valid pointer to a value of type `zx_iommu_desc_stub_t`.
*desc_size* must be `sizeof(zx_iommu_desc_stub_t)`.

## Rights

*resource* must have resource kind `ZX_RSRC_KIND_SYSTEM` and resource base
`ZX_RSRC_SYSTEM_IOMMU_BASE`.

## Return value

`zx_iommu_create()` returns `ZX_OK` and a handle to the new IOMMU
(via *out*) on success.  In the event of failure, a negative error value
is returned.

## Errors

`ZX_ERR_BAD_HANDLE`  *resource* is not a valid handle.

`ZX_ERR_WRONG_TYPE`  *resource* is not a resource handle.

`ZX_ERR_ACCESS_DENIED`  *resource* handle does not have sufficient privileges.

`ZX_ERR_NOT_SUPPORTED` *type* is not a defined value or is not
supported on this system.

`ZX_ERR_INVALID_ARGS`  *desc_size* is larger than `ZX_IOMMU_MAX_DESC_LEN`,
*desc* is an invalid pointer, *out* is an invalid pointer, or the contents of
*desc* are not valid for the given *type*.

`ZX_ERR_NO_MEMORY`  Failure due to lack of memory.
There is no good way for userspace to handle this (unlikely) error.
In a future build this error will no longer occur.

## See also

 - [`zx_bti_create()`]
 - [`zx_bti_pin()`]
 - [`zx_pmt_unpin()`]

[`zx_bti_create()`]: bti_create.md
[`zx_bti_pin()`]: bti_pin.md
[`zx_pmt_unpin()`]: pmt_unpin.md