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TX SKBs will have their buffers DMA mapped with the device. Each buffer
will have at least one TX descriptor associated. Each SKB will also have
a metadata descriptor.
Each TX queue maintains an array of `gve_tx_pending_packet_dqo` objects.
Every TX SKB will have an associated pending_packet object. A TX SKB's
descriptors will use its pending_packet's index as the completion tag,
which will be returned on the TX completion queue.
The device implements a "flow-miss model". Most packets will simply
receive a packet completion. The flow-miss system may choose to process
a packet based on its contents. A TX packet which experiences a flow
miss would receive a miss completion followed by a later reinjection
completion. The miss-completion is received when the packet starts to be
processed by the flow-miss system and the reinjection completion is
received when the flow-miss system completes processing the packet and
sends it on the wire.
Notable mentions:
- Buffers may be freed after receiving the miss-completion, but in order
to avoid packet reordering, we do not complete the SKB until receiving
the reinjection completion.
- The driver must robustly handle the unlikely scenario where a miss
completion does not have an associated reinjection completion. This is
accomplished by maintaining a list of packets which have a pending
reinjection completion. After a short timeout (5 seconds), the
SKB and buffers are released and the pending_packet is moved to a
second list which has a longer timeout (60 seconds), where the
pending_packet will not be reused. When the longer timeout elapses,
the driver may assume the reinjection completion would never be
received and the pending_packet may be reused.
- Completion handling is triggered by an interrupt and is done in the
NAPI poll function. Because the TX path and completion exist in
different threading contexts they maintain their own lists for free
pending_packet objects. The TX path uses a lock-free approach to steal
the list from the completion path.
- Both the TSO context and general context descriptors have metadata
bytes. The device requires that if multiple descriptors contain the
same field, each descriptor must have the same value set for that
field.
Signed-off-by: Bailey Forrest <bcf@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Catherine Sullivan <csully@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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When interrupts are first enabled, we also set the ratelimits, which
will be static for the entire usage of the device.
Signed-off-by: Bailey Forrest <bcf@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Catherine Sullivan <csully@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Allocate the buffer and completion ring structures. Do not populate the
rings yet. That will happen in the respective rx and tx datapath
follow-on patches
Signed-off-by: Bailey Forrest <bcf@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Catherine Sullivan <csully@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Add napi netdev device registration, interrupt handling and initial tx
and rx polling stubs. The stubs will be filled in follow-on patches.
Also:
- LRO feature advertisement and handling
- Also update ethtool logic
Signed-off-by: Bailey Forrest <bcf@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Catherine Sullivan <csully@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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