Re: [PATCH RFC 12/12] vdpa_sim_blk: implement ramdisk behaviour

[Stefano Garzarella]

On Tue, Nov 17, 2020 at 11:36:36AM +0000, Stefan Hajnoczi wrote:
> On Fri, Nov 13, 2020 at 02:47:12PM +0100, Stefano Garzarella wrote:
> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> > index 8e41b3ab98d5..68e74383322f 100644
> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> > @@ -7,6 +7,7 @@
> >   */
> >
> >  #include <linux/module.h>
> > +#include <linux/blkdev.h>
> >  #include <uapi/linux/virtio_blk.h>
> >
> >  #include "vdpa_sim.h"
> > @@ -24,10 +25,137 @@
> >
> >  static struct vdpasim *vdpasim_blk_dev;
> >
> > +static int vdpasim_blk_handle_req(struct vdpasim *vdpasim,
> > +				  struct vdpasim_virtqueue *vq)
>
> This function has a non-standard int return value. Please document it.

Yes, I'll do.

> > +{
> > +	size_t wrote = 0, to_read = 0, to_write = 0;
> > +	struct virtio_blk_outhdr hdr;
> > +	uint8_t status;
> > +	uint32_t type;
> > +	ssize_t bytes;
> > +	loff_t offset;
> > +	int i, ret;
> > +
> > +	vringh_kiov_cleanup(&vq->riov);
> > +	vringh_kiov_cleanup(&vq->wiov);
> > +
> > +	ret = vringh_getdesc_iotlb(&vq->vring, &vq->riov, &vq->wiov,
> > +				   &vq->head, GFP_ATOMIC);
> > +	if (ret != 1)
> > +		return ret;
> > +
> > +	for (i = 0; i < vq->wiov.used; i++)
> > +		to_write += vq->wiov.iov[i].iov_len;
> > +	to_write -= 1; /* last byte is the status */
>
> What if vq->wiov.used == 0?

Right, we should discard the descriptor.

> > +
> > +	for (i = 0; i < vq->riov.used; i++)
> > +		to_read += vq->riov.iov[i].iov_len;
> > +
> > +	bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->riov, &hdr, sizeof(hdr));
> > +	if (bytes != sizeof(hdr))
> > +		return 0;
> > +
> > +	to_read -= bytes;
> > +
> > +	type = le32_to_cpu(hdr.type);
> > +	offset = le64_to_cpu(hdr.sector) << SECTOR_SHIFT;
> > +	status = VIRTIO_BLK_S_OK;
> > +
> > +	switch (type) {
> > +	case VIRTIO_BLK_T_IN:
> > +		if (offset + to_write > VDPASIM_BLK_CAPACITY << SECTOR_SHIFT) {
>
> Integer overflow is not handled.

I'll fix.

Thanks,
Stefano