Re: [PATCH 5/8] xen/netfront: read response from backend only once

[Juergen Gross]

On 17.05.21 16:20, Jan Beulich wrote:

On 13.05.2021 12:02, Juergen Gross wrote:

In order to avoid problems in case the backend is modifying a response
on the ring page while the frontend has already seen it, just read the
response into a local buffer in one go and then operate on that buffer
only.

Signed-off-by: Juergen Gross <jgr...@suse.com>

Reviewed-by: Jan Beulich <jbeul...@suse.com>
with one remark:

@@ -830,24 +830,22 @@ static int xennet_get_extras(struct netfront_queue *queue,
                        break;
                }

-                       RING_GET_RESPONSE(&queue->rx, ++cons);
+               RING_COPY_RESPONSE(&queue->rx, ++cons, &extra);

-                            extra->type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
+               if (unlikely(!extra.type ||
+                            extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
                        if (net_ratelimit())
                                dev_warn(dev, "Invalid extra type: %d\n",
-                                       extra->type);
+                                       extra.type);
                        err = -EINVAL;
                } else {
-                       memcpy(&extras[extra->type - 1], extra,
-                              sizeof(*extra));
+                       memcpy(&extras[extra.type - 1], &extra, sizeof(extra));

- extra = (struct xen_netif_extra_info *) - if (unlikely(!extra->type ||

Maybe take the opportunity and switch to (type safe) structure
assignment?

Yes, good idea.


Juergen

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