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

[Duan, Zhenzhong]

Hi Markus,

>-----Original Message-----
>From: Markus Armbruster <armbru@redhat.com>
>Sent: Monday, October 16, 2023 6:01 PM
>Subject: Re: [PATCH v2 17/27] backends/iommufd: Introduce the iommufd object
>
>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?

Yes, will fix.

>
>> +#
>> +# 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?

Will add more comments here, thanks for point out.

>
>> +#
>> +# Since: 7.2
>
>Since: 8.2.

Yes.

>
>> +##
>> +{ '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.

Will fix.

>
>> @@ -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.

Will fix.

Thanks
Zhenzhong

>
>>    } }
>>
>>  ##
>
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