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SubjectRe: [PATCH net-next] xen-netback: support dynamic unbind/bind
On Mon, Dec 23, 2019 at 09:59:23AM +0000, Paul Durrant wrote:
[...]
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index f15ba3de6195..0c8a02a1ead7 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -585,6 +585,7 @@ int xenvif_connect_ctrl(struct xenvif *vif, grant_ref_t ring_ref,
> struct net_device *dev = vif->dev;
> void *addr;
> struct xen_netif_ctrl_sring *shared;
> + RING_IDX rsp_prod, req_prod;
> int err;
>
> err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(vif),
> @@ -593,7 +594,14 @@ int xenvif_connect_ctrl(struct xenvif *vif, grant_ref_t ring_ref,
> goto err;
>
> shared = (struct xen_netif_ctrl_sring *)addr;
> - BACK_RING_INIT(&vif->ctrl, shared, XEN_PAGE_SIZE);
> + rsp_prod = READ_ONCE(shared->rsp_prod);
> + req_prod = READ_ONCE(shared->req_prod);
> +
> + BACK_RING_ATTACH(&vif->ctrl, shared, rsp_prod, XEN_PAGE_SIZE);
> +
> + err = -EIO;
> + if (req_prod - rsp_prod > RING_SIZE(&vif->ctrl))
> + goto err_unmap;

I think it makes more sense to attach the ring after this check has been
done, but I can see you want to structure code like this to reuse the
unmap error path.

So:

Reviewed-by: Wei Liu <wei.liu@kernel.org>

Nice work btw.

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