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SubjectRe: [PATCH v2 16/16] net: Add support for networking over Thunderbolt cable
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From: Mika Westerberg <mika.westerberg@linux.intel.com>
Date: Mon, 25 Sep 2017 14:07:38 +0300

> +struct thunderbolt_ip_header {
> + u32 route_hi;
> + u32 route_lo;
> + u32 length_sn;
> + uuid_t uuid;
> + uuid_t initiator_uuid;
> + uuid_t target_uuid;
> + u32 type;
> + u32 command_id;
> +} __packed;

Again, the __packed attribute should not be necessary and needs to be
removed.

> +static void tbnet_pull_tail(struct sk_buff *skb)
> +{
> + skb_frag_t *frag = &skb_shinfo(skb)->frags[0];
> + unsigned int pull_len;
> + void *hdr;
> +
> + hdr = skb_frag_address(frag);
> + pull_len = eth_get_headlen(hdr, TBNET_RX_HDR_SIZE);
> +
> + /* Align pull length to size of long to optimize memcpy performance */
> + skb_copy_to_linear_data(skb, hdr, ALIGN(pull_len, sizeof(long)));

You do not need to copy here, instead you can build SKB's where the
skb->data points directly at the head of your first frag page memory.

See build_skb().

> + skb = net->skb;
> + if (!skb) {
> + skb = netdev_alloc_skb_ip_align(net->dev,
> + TBNET_RX_HDR_SIZE);
> + net->skb = skb;
> + }
> + if (!skb)
> + break;
> +
> + /* Single small buffer we can copy directly to the
> + * header part of the skb.
> + */
> + if (hdr->frame_count == 1 && frame_size <= TBNET_RX_HDR_SIZE) {

Here you would use build_skb() instead of netdev_alloc_skb*() for the first
frag, and keep the existing code tacking on subsequent frags using
skb_add_Rx_frag().

> + ret = register_netdev(dev);
> + if (ret) {
> + free_netdev(dev);
> + return ret;
> + }
> +
> + net->handler.uuid = &tbnet_svc_uuid;
> + net->handler.callback = tbnet_handle_packet,
> + net->handler.data = net;
> + tb_register_protocol_handler(&net->handler);
> +
> + tb_service_set_drvdata(svc, net);

There could be races here.

At the exact moment you call register_netdev(), your device can be
brought UP, packets transmitted, etc. You entire set of driver code
paths can be executed.

The rest of those initializations after register_netdev() probably
are needed by the rest of the driver to function properly, so may
need to happen before register_netdev() publishes the device to the
entire world.

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