Shailend Chand d438b4ef0c gve: Add DQO RDA support ... DQO is the descriptor format for our next generation virtual NIC. It is necessary to make full use of the hardware bandwidth on many newer GCP VM shapes. One major change with DQO from its predecessor GQI is that it uses dual descriptor rings for both TX and RX queues. The TX path uses a descriptor ring to send descriptors to HW, and receives packet completion events on a TX completion ring. The RX path posts buffers to HW using an RX descriptor ring and receives incoming packets on an RX completion ring. In GQI-QPL, the hardware could not access arbitrary regions of guest memory, which is why there was a pre-negotitated bounce buffer (QPL: Queue Page List). DQO-RDA has no such limitation. "RDA" is in contrast to QPL and stands for "Raw DMA Addressing" which just means that HW does not need a fixed bounce buffer and can DMA arbitrary regions of guest memory. A subsequent patch will introduce the DQO-QPL datapath that uses the same descriptor format as in this patch, but will have a fixed bounce buffer. Signed-off-by: Shailend Chand <shailend@google.com> Reviewed-by: markj MFC-after: 2 weeks Differential Revision: https://reviews.freebsd.org/D46690		2024-11-06 15:06:41 +00:00
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