On Tue, May 02, 2023 at 04:50:50PM +0200, Stefano Garzarella wrote: > The virtio-blk-vhost-vdpa driver in libblkio 1.3.0 supports the new > 'fd' property. Let's expose this to the user, so the management layer > can pass the file descriptor of an already opened vhost-vdpa character > device. This is useful especially when the device can only be accessed > with certain privileges. > > Signed-off-by: Stefano Garzarella <sgarz...@redhat.com> > --- > > Notes: > As an alternative we could support passing `/dev/fdset/N` via 'path', > always opening the path with qemu_open() and passing the fd to the > libblkio driver. > I preferred to add a new parameter though, because the code is > simpler without changing how path works (alternatively we should check > first if fd is supported by the driver or not). > > What do you think?
I think the approach in this patch is fine.
>
> Thanks,
> Stefano
>
> qapi/block-core.json | 6 +++++-
> block/blkio.c | 45 +++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index b57978957f..9f70777d49 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -3841,10 +3841,14 @@
> #
> # @path: path to the vhost-vdpa character device.
> #
> +# @fd: file descriptor of an already opened vhost-vdpa character device.
> +# (Since 8.1)
> +#
> # Since: 7.2
> ##
> { 'struct': 'BlockdevOptionsVirtioBlkVhostVdpa',
> - 'data': { 'path': 'str' },
> + 'data': { '*path': 'str',
> + '*fd': 'str' },
> 'if': 'CONFIG_BLKIO' }
>
> ##
> diff --git a/block/blkio.c b/block/blkio.c
> index 0cdc99a729..98394b5745 100644
> --- a/block/blkio.c
> +++ b/block/blkio.c
> @@ -694,6 +694,49 @@ static int blkio_virtio_blk_common_open(BlockDriverState
> *bs,
> return 0;
> }
>
> +static int blkio_virtio_blk_vhost_vdpa_open(BlockDriverState *bs,
> + QDict *options, int flags, Error **errp)
> +{
> + const char *path = qdict_get_try_str(options, "path");
> + const char *fd_str = qdict_get_try_str(options, "fd");
> + BDRVBlkioState *s = bs->opaque;
> + int ret;
> +
> + if (path && fd_str) {
> + error_setg(errp, "'path' and 'fd' options are mutually exclusive");
> + return -EINVAL;
> + }
> +
> + if (!path && !fd_str) {
> + error_setg(errp, "none of 'path' or 'fd' options was specified");
> + return -EINVAL;
> + }
> +
> + if (path) {
> + ret = blkio_set_str(s->blkio, "path", path);
> + qdict_del(options, "path");
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "failed to set path: %s",
> + blkio_get_error_msg());
> + return ret;
> + }
> + } else {
> + ret = blkio_set_str(s->blkio, "fd", fd_str);
monitor_fd_param() is used by vhost-net, vhost-vsock, vhost-scsi, etc.
I think QEMU should parse the fd string and resolve it to a file
descriptor so the fd passing syntax matches the other vhost devices.
signature.asc
Description: PGP signature
