gve: Fix TX livelock

Before this change the transmit taskqueue would enqueue itself when it
cannot find space on the NIC ring with the hope that eventually space
would be made. This results in the f

gve: Fix TX livelock

Before this change the transmit taskqueue would enqueue itself when it
cannot find space on the NIC ring with the hope that eventually space
would be made. This results in the following livelock that only occurs
after passing ~200Gbps of TCP traffic for many hours:

100% CPU
┌───────────┐wait on ┌──────────┐ ┌───────────┐
│user thread│ cpu │gve xmit │wait on │gve cleanup│
│with mbuf ├────────►│taskqueue ├────────►│taskqueue │
│uma lock │ │ │ NIC ring│ │
└───────────┘ └──────────┘ space └─────┬─────┘
▲ │
│ wait on mbuf uma lock │
└───────────────────────────────────────────┘

Further details about the livelock are available on
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=281560.

After this change, the transmit taskqueue no longer spins till there is
room on the NIC ring. It instead stops itself and lets the
completion-processing taskqueue wake it up.

Since I'm touching the trasnmit taskqueue I've also corrected the name
of a counter and also fixed a bug where EINVAL mbufs were not being
freed and were instead living forever on the bufring.

Signed-off-by: Shailend Chand <shailend@google.com>
Reviewed-by: markj
MFC-after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D47138

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gve: Add DQO QPL 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.

This patch extends

gve: Add DQO QPL 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.

This patch extends the previously introduced DQO descriptor format
with a "QPL" mode. QPL stands for Queue Page List and refers to
the fact that the hardware cannot access arbitrary regions of the
host memory and instead expects a fixed bounce buffer comprising
of a list of pages.

The QPL aspects are similar to the already existing GQI queue
queue format: in that the mbufs being input in the Rx path have
external storage in the form of vm pages attached to them; and
in the Tx path we always copy the mbuf payload into QPL pages.

Signed-off-by: Shailend Chand <shailend@google.com>
Reviewed-by: markj
MFC-after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D46691

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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 w

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

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Check for errors when detaching children first, not last

These detach routines in these drivers all ended with 'return
(bus_generic_detach())' meaning that if any child device failed to
detach, the

Check for errors when detaching children first, not last

These detach routines in these drivers all ended with 'return
(bus_generic_detach())' meaning that if any child device failed to
detach, the parent driver was left in a mostly destroyed state, but
still marked attached. Instead, bus drivers should detach child
drivers first and return errors before destroying driver state in the
parent.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D47387

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