netdev - Re: [PATCH net-next v5 0/6] Remove RTNL lock protection of CVQ

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Date: Fri, 26 Apr 2024 11:53:31 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Daniel Jurgens <danielj@...dia.com>, netdev@...r.kernel.org, 
	jasowang@...hat.com, mst@...hat.com
Cc: xuanzhuo@...ux.alibaba.com, virtualization@...ts.linux.dev, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, jiri@...dia.com
Subject: Re: [PATCH net-next v5 0/6] Remove RTNL lock protection of CVQ

On Tue, 2024-04-23 at 06:57 +0300, Daniel Jurgens wrote:
> Currently the buffer used for control VQ commands is protected by the
> RTNL lock. Previously this wasn't a major concern because the control VQ
> was only used during device setup and user interaction. With the recent
> addition of dynamic interrupt moderation the control VQ may be used
> frequently during normal operation.
> 
> This series removes the RNTL lock dependency by introducing a mutex
> to protect the control buffer and writing SGs to the control VQ.
> 
> v5:
> 	- Changed cvq_lock to a mutex.
> 	- Changed dim_lock to mutex, because it's held taking
> 	  the cvq_lock.
> 	- Use spin/mutex_lock/unlock vs guard macros.
> v4:
> 	- Protect dim_enabled with same lock as well intr_coal.
> 	- Rename intr_coal_lock to dim_lock.
> 	- Remove some scoped_guard where the error path doesn't
> 	  have to be in the lock.
> v3:
> 	- Changed type of _offloads to __virtio16 to fix static
> 	  analysis warning.
> 	- Moved a misplaced hunk to the correct patch.
> v2:
> 	- New patch to only process the provided queue in
> 	  virtnet_dim_work
> 	- New patch to lock per queue rx coalescing structure.

I had only some minor comments, possibly overall worth another
iteration.

More importantly, this deserves an explicit ack from the virtio crew.
@Jason, @Michael: could you please have a look?

Thanks!

Paolo