Re: [PATCH RFC 04/12] vdpa: add vdpa simulator for block device

Stefano Garzarella
2020-11-17T14:16:39Z

On Tue, Nov 17, 2020 at 11:11:21AM +0000, Stefan Hajnoczi wrote:
>On Fri, Nov 13, 2020 at 02:47:04PM +0100, Stefano Garzarella wrote:
>> +static void vdpasim_blk_work(struct work_struct *work)
>> +{
>> + struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
>> + u8 status = VIRTIO_BLK_S_OK;
>> + int i;
>> +
>> + spin_lock(&vdpasim->lock);
>> +
>> + if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK))
>> + goto out;
>> +
>> + for (i = 0; i < VDPASIM_BLK_VQ_NUM; i++) {
>> + struct vdpasim_virtqueue *vq = &vdpasim->vqs[i];
>> +
>> + if (!vq->ready)
>> + continue;
>> +
>> + while (vringh_getdesc_iotlb(&vq->vring, &vq->iov, &vq->iov,
>> + &vq->head, GFP_ATOMIC) > 0) {
>> +
>> + int write;
>> +
>> + vq->iov.i = vq->iov.used - 1;
>> + write = vringh_iov_push_iotlb(&vq->vring, &vq->iov, &status, 1);
>> + if (write <= 0)
>> + break;
>
>We're lucky the guest driver doesn't crash after VIRTIO_BLK_T_GET_ID? :)

The crash could happen if the simulator doesn't put the string
terminator, but in virtio_blk.c, the serial_show() initialize the buffer
putting the string terminator in the VIRTIO_BLK_ID_BYTES element:

buf[VIRTIO_BLK_ID_BYTES] = '\0';
err = virtblk_get_id(disk, buf);

This should prevent the issue, right?

However in the last patch of this series I implemented
VIRTIO_BLK_T_GET_ID support :-)

Thanks,
Stefano