On Fri, Feb 01, 2019 at 05:27:37PM +0300, Ilya Maximets wrote:
On 01.02.2019 13:03, Jens Freimann wrote:
+ if (host_features & (1ULL << VIRTIO_NET_F_MTU)) {
+ uint32_t ether_hdr_len = ETHER_HDR_LEN + VLAN_TAG_LEN +
+ hw->vtnet_hdr_size;
+ if (dev->data->dev_conf.rxmode.max_rx_pkt_len <=
+ hw->max_mtu + ether_hdr_len)
+ dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_JUMBO_FRAME;
+ } else {
+ dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_JUMBO_FRAME;
+ }
+
As I wrote for v3, hw->max_mtu already calculated taking VIRTIO_NET_F_MTU
into account. If VIRTIO_NET_F_MTU is not set, hw->max_mtu is equal to
"VIRTIO_MAX_RX_PKTLEN - ETHER_HDR_LEN - VLAN_TAG_LEN - hw->vtnet_hdr_size".
i.e. "hw->max_mtu + ether_hdr_len" equal to VIRTIO_MAX_RX_PKTLEN which is
larger or equal to rxmode.max_rx_pkt_len.
So, there is no need to check for VIRTIO_NET_F_MTU here. You may just perform
same check for both cases.
I should read more carefully :). I think I get what you mean now.
hw->max_mtu already includes ether_hdr_len, so it doesn't need
re-calculation here. And in case of VIRTIO_NET_F_MTU the mtu is
checked during feature negotiation.
So it basically boils down to
if (dev->data->dev_conf.rxmode.max_rx_pkt_len <= w->max_mtu)
dev_info->rx_offload_capa |= DEV_RX_OFFLOAD_JUMBO_FRAME;
This doesn't give any performance or so, but will simplify the code.
Thanks for the review!
regards,
Jens
