Re: [PATCH v2 17/27] backends/iommufd: Introduce the iommufd object

[Markus Armbruster <armbru@redhat.com>]

Zhenzhong Duan <zhenzhong.duan@intel.com> writes:

> From: Eric Auger <eric.auger@redhat.com>
>
> Introduce an iommufd object which allows the interaction
> with the host /dev/iommu device.
>
> The /dev/iommu can have been already pre-opened outside of qemu,
> in which case the fd can be passed directly along with the
> iommufd object:
>
> This allows the iommufd object to be shared accross several
> subsystems (VFIO, VDPA, ...). For example, libvirt would open
> the /dev/iommu once.
>
> If no fd is passed along with the iommufd object, the /dev/iommu
> is opened by the qemu code.
>
> The CONFIG_IOMMUFD option must be set to compile this new object.
>
> Suggested-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  MAINTAINERS              |   7 +
>  qapi/qom.json            |  18 ++-
>  include/sysemu/iommufd.h |  46 +++++++
>  backends/iommufd-stub.c  |  59 +++++++++
>  backends/iommufd.c       | 268 +++++++++++++++++++++++++++++++++++++++
>  backends/Kconfig         |   4 +
>  backends/meson.build     |   5 +
>  backends/trace-events    |  12 ++
>  qemu-options.hx          |  13 ++
>  9 files changed, 431 insertions(+), 1 deletion(-)
>  create mode 100644 include/sysemu/iommufd.h
>  create mode 100644 backends/iommufd-stub.c
>  create mode 100644 backends/iommufd.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 9e7dec4a58..a7cdeb7825 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2081,6 +2081,13 @@ F: hw/vfio/ap.c
>  F: docs/system/s390x/vfio-ap.rst
>  L: qemu-s390x@nongnu.org
>  
> +iommufd
> +M: Yi Liu <yi.l.liu@intel.com>
> +M: Eric Auger <eric.auger@redhat.com>
> +S: Supported
> +F: backends/iommufd.c
> +F: include/sysemu/iommufd.h
> +
>  vhost
>  M: Michael S. Tsirkin <mst@redhat.com>
>  S: Supported
> diff --git a/qapi/qom.json b/qapi/qom.json
> index c53ef978ff..3f964e57f5 100644
> --- a/qapi/qom.json
> +++ b/qapi/qom.json
> @@ -794,6 +794,18 @@
>  { 'struct': 'VfioUserServerProperties',
>    'data': { 'socket': 'SocketAddress', 'device': 'str' } }
>  
> +##
> +# @IOMMUFDProperties:
> +#
> +# Properties for IOMMUFDbackend objects.

This is the only occurence of "IOMMUFDbackend".  Do you mean iommufd?

> +#
> +# fd: file descriptor name

Awfully terse.  Like many existing FOOProperties.  Would it make sense
to document what objects of type iommufd are good for, and how they use
@fd?  Or is it already documented elsewhere?

> +#
> +# Since: 7.2

Since: 8.2.

> +##
> +{ 'struct': 'IOMMUFDProperties',
> +        'data': { '*fd': 'str' } }
> +
>  ##
>  # @RngProperties:
>  #
> @@ -948,6 +960,8 @@
>      'qtest',
>      'rng-builtin',
>      'rng-egd',
> +    { 'name': 'iommufd',
> +      'if': 'CONFIG_IOMMUFD' },
>      { 'name': 'rng-random',
>        'if': 'CONFIG_POSIX' },
>      'secret',

Please keep the members sorted.

> @@ -1029,7 +1043,9 @@
>        'tls-creds-x509':             'TlsCredsX509Properties',
>        'tls-cipher-suites':          'TlsCredsProperties',
>        'x-remote-object':            'RemoteObjectProperties',
> -      'x-vfio-user-server':         'VfioUserServerProperties'
> +      'x-vfio-user-server':         'VfioUserServerProperties',
> +      'iommufd':                    { 'type': 'IOMMUFDProperties',
> +                                      'if': 'CONFIG_IOMMUFD' }

Likewise.

>    } }
>  
>  ##

[...]