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