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

[Stefano Garzarella]

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