[Intel-wired-lan] [PATCH 14/15] fm10k: introduce a message queue for MAC/VLAN messages

[Keller, Jacob E]

> -----Original Message-----
> From: Keller, Jacob E
> Sent: Thursday, June 01, 2017 3:41 PM
> To: Intel Wired LAN <intel-wired-lan at lists.osuosl.org>
> Cc: Keller, Jacob E <jacob.e.keller at intel.com>
> Subject: [PATCH 14/15] fm10k: introduce a message queue for MAC/VLAN
> messages
> 
> Under some circumstances, when dealing with a large number of MAC
> address or VLAN updates at once, the fm10k driver, particularly the VFs
> can overload the mailbox with too many messages at once.
> 
> This results in a mailbox timeout, which causes the driver to initiate
> a reset. During the reset, we re-send all the same messages that
> originally caused the timeout. This results in a cycle of resets each
> triggering a future reset.
> 
> To fix or avoid this, we introduce a workqueue item which monitors
> a queue of MAC and VLAN requests. These requests are queued to the end
> of the list, and we process as a FIFO periodically.
> 
> Initially we only handle requests for the netdev, but we do handle
> unicast MAC addresses, multicast MAC addresses, and update VLAN
> requests.
> 
> A future patch will add support to use this queue for handling MAC
> update requests from the VF<->PF mailbox.
> 
> The MAC/VLAN work item will keep checking to make sure that each request
> does not overflow the mailbox and cause a timeout. If it might, then the
> work item will reschedule itself a short time later. This avoids any
> reset cycle, since we never send the message if the mailbox is not
> ready.
> 
> As an alternative, we tried increasing the mailbox message FIFO, but
> this just delays the problem and results in needless memory waste on the
> system. Our new message queue is dynamically allocated so only uses as
> much memory as it needs. Additionally, it need not be contiguous like
> the Tx and Rx FIFOs.
> 
> Note that this patch chose to only create a queue for MAC and VLAN
> messages, since these are the only messages sent in a large enough
> volume to cause the reset loop. Other messages are very unlikely to
> overflow the mailbox Tx fifo so easily.
> 
> Signed-off-by: Jacob Keller <jacob.e.keller at intel.com>
> ---

Validation found a bug in this patch. I'll be sending a v2 (of only this patch) that should apply in-place of the current version on your queue.

Regards,
Jake