On Tue, Feb 15, 2022 at 06:59:41PM +0800, Xie Yongji wrote: > This implements a VDUSE block backends based on > the libvduse library. We can use it to export the BDSs > for both VM and container (host) usage. > > The new command-line syntax is: > > $ qemu-storage-daemon \ > --blockdev file,node-name=drive0,filename=test.img \ > --export vduse-blk,node-name=drive0,id=vduse-export0,writable=on > > After the qemu-storage-daemon started, we need to use > the "vdpa" command to attach the device to vDPA bus: > > $ vdpa dev add name vduse-export0 mgmtdev vduse
The per-QEMU export id is used as the global vdpa device name. If this
becomes a problem in the future then a new --export
vduse-blk,vdpa-dev-name= option can be added.
> + case VIRTIO_BLK_T_GET_ID: {
> + size_t size = MIN(iov_size(&elem->in_sg[0], in_num),
> + VIRTIO_BLK_ID_BYTES);
> + snprintf(elem->in_sg[0].iov_base, size, "%s", vblk_exp->export.id);
Please use iov_from_buf(). The driver is allowed to submit as many
in_sg[] elements as it wants and a compliant virtio-blk device
implementation must support that.
Here is the VIRTIO specification section that covers message framing:
https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-280004
> + features = (1ULL << VIRTIO_F_IOMMU_PLATFORM) |
> + (1ULL << VIRTIO_F_VERSION_1) |
> + (1ULL << VIRTIO_RING_F_EVENT_IDX) |
> + (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
> + (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
> + (1ULL << VIRTIO_BLK_F_SIZE_MAX) |
> + (1ULL << VIRTIO_BLK_F_SEG_MAX) |
> + (1ULL << VIRTIO_BLK_F_TOPOLOGY) |
> + (1ULL << VIRTIO_BLK_F_BLK_SIZE);
The VIRTIO_F_ and VIRTIO_RING_F_ feature bits report the capabilities of
libvduse. They should probably be defined in libvduse. That way no
changes to vduse-blk.c are required when libvduse changes:
features = LIBVDUSE_VIRTIO_FEATURES |
(1ULL << VIRTIO_BLK_F_SIZE_MAX) |
...;
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