Re: [PATCH RFC 12/15] hw/virtio/vhost-user: send isolation regions to device

On Tue, Jul 28, 2026 at 12:16 PM Stefan Hajnoczi <[email protected]> wrote:
>
> >
> > -__attribute__((unused))
> > +struct iova_tree_traversal_args {
>
> QEMU coding style:
>
>   typedef struct {
>       ...
>   } IOVATreeTraversalArgs;
>

...

Got it!  This is now fixed.

> > +    VhostUserMsg *msg;
> > +    struct vhost_user *u;
> > +    int *fds;
> > +    size_t *fd_num;
>
> This field is also used to index into msg->payload.memory.regions[], so
> "fd_num" is a misnomer. I suggest something like "region_idx" or just
> "idx".
>

I'll rename it to idx since it acts as an index to multiple arrays.

> > +};
> > +
> > +static gboolean vhost_user_iova_tree_traverse_funct(gpointer key,
> > +                                                    gpointer value,
> > +                                                    gpointer data)
> > +{
> > +    struct iova_tree_traversal_args *args = data;
> > +    struct vhost_memory_region msg_region;
> > +    VhostUserMemoryRegion region_buffer;
> > +    DMAMap *map = key;
> > +    args->fds[*args->fd_num] = args->u->iso_memory.iso_fd;
> > +
> > +    msg_region.guest_phys_addr = map->iova;
> > +    msg_region.memory_size = map->size + 1;
> > +    msg_region.userspace_addr = map->iova;
> > +    vhost_user_fill_msg_region_iso(&region_buffer, args->u, &msg_region);
> > +    args->msg->payload.memory.regions[*args->fd_num] = region_buffer;
>
> I'm confused by this code. VhostUserMemoryRegion region_buffer is the
> vhost-user protocol struct that is being filled in, but there is also a
> struct vhost_memory_region msg_region from the Linux kernel headers?
>
> msg_region and vhost_user_fill_msg_region_iso() make it harder to see
> what is going on. Can you open code the region_buffer struct field
> assignments instead?
>

I've consolidated this code significantly now.  Will delete
vhost_user_fill_msg_region_iso as it's logic has been incorporated in
the traversal callback.