From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Fastabend Subject: Re: [net PATCH v5 1/6] virtio_net: use dev_kfree_skb for small buffer XDP receive Date: Tue, 24 Jan 2017 20:02:29 -0800 Message-ID: <58882355.70307@gmail.com> References: <20170117221443.20280.62546.stgit@john-Precision-Tower-5810> <20170117221950.20280.39496.stgit@john-Precision-Tower-5810> <20170123230809-mutt-send-email-mst@kernel.org> <20170124.144328.2195698124358175034.davem@davemloft.net> <20170124215412-mutt-send-email-mst@kernel.org> <20170125051810-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: David Miller , john.r.fastabend@intel.com, netdev@vger.kernel.org, alexei.starovoitov@gmail.com, daniel@iogearbox.net To: "Michael S. Tsirkin" , Jason Wang Return-path: Received: from mail-pg0-f68.google.com ([74.125.83.68]:34225 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751137AbdAYECq (ORCPT ); Tue, 24 Jan 2017 23:02:46 -0500 Received: by mail-pg0-f68.google.com with SMTP id 3so635344pgj.1 for ; Tue, 24 Jan 2017 20:02:46 -0800 (PST) In-Reply-To: <20170125051810-mutt-send-email-mst@kernel.org> Sender: netdev-owner@vger.kernel.org List-ID: On 17-01-24 07:23 PM, Michael S. Tsirkin wrote: > On Wed, Jan 25, 2017 at 10:57:12AM +0800, Jason Wang wrote: >> >> >> On 2017年01月25日 04:08, Michael S. Tsirkin wrote: >>> On Tue, Jan 24, 2017 at 02:43:28PM -0500, David Miller wrote: >>>> From: "Michael S. Tsirkin" >>>> Date: Mon, 23 Jan 2017 23:08:35 +0200 >>>> >>>>> On Tue, Jan 17, 2017 at 02:19:50PM -0800, John Fastabend wrote: >>>>>> In the small buffer case during driver unload we currently use >>>>>> put_page instead of dev_kfree_skb. Resolve this by adding a check >>>>>> for virtnet mode when checking XDP queue type. Also name the >>>>>> function so that the code reads correctly to match the additional >>>>>> check. >>>>>> >>>>>> Fixes: bb91accf2733 ("virtio-net: XDP support for small buffers") >>>>>> Signed-off-by: John Fastabend >>>>>> Acked-by: Jason Wang >>>>> Acked-by: Michael S. Tsirkin >>>>> >>>>> I think we definitely want this one in -net as it's >>>>> a bugfix. >>>> This whole series is a bug fix, we must have adjust_header XDP >>>> support in the virtio_net driver before v4.10 goes out, it is >>>> a requires base feature for XDP. >>> I have to say device resets outside probe have a huge potential >>> to uncover hypervisor bugs. >> >> Maybe not if it reuses most of current codes? Since we've already used them >> in sleep or hibernation? >> >> Thanks > > Except almost no one uses sleep or hybernate with VMs. I'm not saying > it's a bad idea, just that it needs a lot of testing before release and > we won't get enough if we merge at this point. > Then it would seem like a good thing to have another user of these paths and find the bugs versus letting them sit there for some poor folks who do use sleep/hybernate. >>> I am rather uncomfortable >>> doing that after -rc1. >>> >>> How about a module option to disable it by default? >>> We can then ship a partial implementation in 4.10 >>> and work on completing it in 4.11. >>> Ugh I would prefer to avoid module options. This will only happen if users push XDP program into driver anyways. > > To clarify, I'm thinking an option similar to enable_xdp, > and have all packets have a 256 byte headroom for 4.10. An option where? In QEMU side, in driver? Is the reset really that bad, coming from a hardware driver side lots of configuration changes can cause resets. I agree its not overly elegant but could follow on patches be used to make it prettier if possible. I know folks prefer to avoid tuning knobs but I think exposing the headroom configuration to users might not be a bad idea. After all these same users are already programming maps and ebpf codes. A simple tuning knob should not be a big deal and reasonable defaults would of course be used. That is a net-next debate though. > > Consider our options for 4.11. > Finally just to point out here are the drivers with XDP support on latest net tree, mlx/mlx5 mlx/mlx4 qlogic/qede netronome/nfp virtio_net And here is the list of adjust header support, mlx/mlx4 So we currently have the same feature gap on all the other drivers except one. Although I do not think that is a very good excuse. Lets figure out what we should do about virtio. Thanks, John