Re: [PATCH v5 02/12] blkio: add libblkio block driver

[Markus Armbruster <armbru@redhat.com>]

Stefan Hajnoczi <stefanha@redhat.com> writes:

> libblkio (https://gitlab.com/libblkio/libblkio/) is a library for
> high-performance disk I/O. It currently supports io_uring,
> virtio-blk-vhost-user, and virtio-blk-vhost-vdpa with additional drivers
> under development.
>
> One of the reasons for developing libblkio is that other applications
> besides QEMU can use it. This will be particularly useful for
> virtio-blk-vhost-user which applications may wish to use for connecting
> to qemu-storage-daemon.
>
> libblkio also gives us an opportunity to develop in Rust behind a C API
> that is easy to consume from QEMU.
>
> This commit adds io_uring, virtio-blk-vhost-user, and
> virtio-blk-vhost-vdpa BlockDrivers to QEMU using libblkio. It will be
> easy to add other libblkio drivers since they will share the majority of
> code.
>
> For now I/O buffers are copied through bounce buffers if the libblkio
> driver requires it. Later commits add an optimization for
> pre-registering guest RAM to avoid bounce buffers.
>
> The syntax is:
>
>   --blockdev io_uring,node-name=drive0,filename=test.img,readonly=on|off,cache.direct=on|off
>
> and:
>
>   --blockdev virtio-blk-vhost-vdpa,node-name=drive0,path=/dev/vdpa...,readonly=on|off
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> Acked-by: Markus Armbruster <armbru@redhat.com>

[...]

> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index f21fa235f2..5aed0dd436 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2951,11 +2951,16 @@
>              'file', 'snapshot-access', 'ftp', 'ftps', 'gluster',
>              {'name': 'host_cdrom', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
>              {'name': 'host_device', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
> -            'http', 'https', 'iscsi',
> +            'http', 'https',
> +            { 'name': 'io_uring', 'if': 'CONFIG_BLKIO' },
> +            'iscsi',
>              'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
>              'preallocate', 'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
>              { 'name': 'replication', 'if': 'CONFIG_REPLICATION' },
> -            'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
> +            'ssh', 'throttle', 'vdi', 'vhdx',
> +            { 'name': 'virtio-blk-vhost-user', 'if': 'CONFIG_BLKIO' },
> +            { 'name': 'virtio-blk-vhost-vdpa', 'if': 'CONFIG_BLKIO' },
> +            'vmdk', 'vpc', 'vvfat' ] }
>  
>  ##
>  # @BlockdevOptionsFile:
> @@ -3678,6 +3683,42 @@
>              '*debug': 'int',
>              '*logfile': 'str' } }
>  
> +##
> +# @BlockdevOptionsIoUring:
> +#
> +# Driver specific block device options for the io_uring backend.
> +#
> +# @filename: path to the image file
> +#
> +# Since: 7.2
> +##
> +{ 'struct': 'BlockdevOptionsIoUring',
> +  'data': { 'filename': 'str' } }
> +
> +##
> +# @BlockdevOptionsVirtioBlkVhostUser:
> +#
> +# Driver specific block device options for the virtio-blk-vhost-user backend.
> +#
> +# @path: path to the vhost-user UNIX domain socket.
> +#
> +# Since: 7.2
> +##
> +{ 'struct': 'BlockdevOptionsVirtioBlkVhostUser',
> +  'data': { 'path': 'str' } }
> +
> +##
> +# @BlockdevOptionsVirtioBlkVhostVdpa:
> +#
> +# Driver specific block device options for the virtio-blk-vhost-vdpa backend.
> +#
> +# @path: path to the vhost-vdpa character device.
> +#
> +# Since: 7.2
> +##
> +{ 'struct': 'BlockdevOptionsVirtioBlkVhostVdpa',
> +  'data': { 'path': 'str' } }
> +

Should these be 'if': 'CONFIG_BLKIO'?

>  ##
>  # @IscsiTransport:
>  #
> @@ -4305,6 +4346,8 @@
>                         'if': 'HAVE_HOST_BLOCK_DEVICE' },
>        'http':       'BlockdevOptionsCurlHttp',
>        'https':      'BlockdevOptionsCurlHttps',
> +      'io_uring':   { 'type': 'BlockdevOptionsIoUring',
> +                      'if': 'CONFIG_BLKIO' },
>        'iscsi':      'BlockdevOptionsIscsi',
>        'luks':       'BlockdevOptionsLUKS',
>        'nbd':        'BlockdevOptionsNbd',
> @@ -4327,6 +4370,12 @@
>        'throttle':   'BlockdevOptionsThrottle',
>        'vdi':        'BlockdevOptionsGenericFormat',
>        'vhdx':       'BlockdevOptionsGenericFormat',
> +      'virtio-blk-vhost-user':
> +                    { 'type': 'BlockdevOptionsVirtioBlkVhostUser',
> +                      'if': 'CONFIG_BLKIO' },
> +      'virtio-blk-vhost-vdpa':
> +                    { 'type': 'BlockdevOptionsVirtioBlkVhostVdpa',
> +                      'if': 'CONFIG_BLKIO' },
>        'vmdk':       'BlockdevOptionsGenericCOWFormat',
>        'vpc':        'BlockdevOptionsGenericFormat',
>        'vvfat':      'BlockdevOptionsVVFAT'

[...]