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

From: Juergen Gross
Date: Mon May 17 2021 - 10:29:03 EST


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 <jgross@xxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one remark:

@@ -830,24 +830,22 @@ static int xennet_get_extras(struct netfront_queue *queue,
break;
}
- extra = (struct xen_netif_extra_info *)
- RING_GET_RESPONSE(&queue->rx, ++cons);
+ RING_COPY_RESPONSE(&queue->rx, ++cons, &extra);
- if (unlikely(!extra->type ||
- 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));

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

Yes, good idea.


Juergen

Attachment: OpenPGP_0xB0DE9DD628BF132F.asc
Description: OpenPGP public key

Attachment: OpenPGP_signature
Description: OpenPGP digital signature