Re: [PATCH net-next v4 2/2] virtio-net: add cond_resched() to the command waiting loop

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>,
	Shannon Nelson <shannon.nelson@amd.com>,
	xuanzhuo@linux.alibaba.com, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org, edumazet@google.com,
	kuba@kernel.org, pabeni@redhat.com, davem@davemloft.net
Subject: Re: [PATCH net-next v4 2/2] virtio-net: add cond_resched() to the command waiting loop
Date: Thu, 27 Jul 2023 05:46:45 -0400	[thread overview]
Message-ID: <20230727054300-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CACGkMEuEFG-vT0xqddRAn2=V+4kayVG7NFVpB96vmecy0TLOWw@mail.gmail.com>

On Thu, Jul 27, 2023 at 04:59:33PM +0800, Jason Wang wrote:
> > They really shouldn't - any NIC that takes forever to
> > program will create issues in the networking stack.
> 
> Unfortunately, it's not rare as the device/cvq could be implemented
> via firmware or software.

Currently that mean one either has sane firmware with a scheduler that
can meet deadlines, or loses ability to report errors back.

> > But if they do they can always set this flag too.
> 
> This may have false negatives and may confuse the management.
> 
> Maybe we can extend the networking core to allow some device specific
> configurations to be done with device specific lock without rtnl. For
> example, split the set_channels to
> 
> pre_set_channels
> set_channels
> post_set_channels
> 
> The device specific part could be done in pre and post without a rtnl lock?
> 
> Thanks

Would the benefit be that errors can be reported to userspace then?
Then maybe.  I think you will have to show how this works for at least
one card besides virtio.

-- 
MST