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 <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

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