From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Samudrala, Sridhar" Subject: Re: [RFC PATCH] virtio_net: Extend virtio to use VF datapath when available Date: Tue, 19 Dec 2017 16:26:02 -0800 Message-ID: References: <20171219174259-mutt-send-email-mst@kernel.org> <20171219095548.61d70d10@xeon-e3> <20171219.132117.666798483874609477.davem@davemloft.net> <20171219104159.30d9caaf@xeon-e3> <344f0afc-b4aa-9f1a-15b8-166ba97d270b@intel.com> <20171219114627.76dac732@xeon-e3> <20171219145345.3c261273@xeon-e3> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: David Miller , mst@redhat.com, netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, alexander.duyck@gmail.com, jesse.brandeburg@intel.com To: Stephen Hemminger Return-path: Received: from mga07.intel.com ([134.134.136.100]:19676 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753439AbdLTA0D (ORCPT ); Tue, 19 Dec 2017 19:26:03 -0500 In-Reply-To: <20171219145345.3c261273@xeon-e3> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 12/19/2017 2:53 PM, Stephen Hemminger wrote: > On Tue, 19 Dec 2017 14:37:50 -0800 > "Samudrala, Sridhar" wrote: > >> On 12/19/2017 11:46 AM, Stephen Hemminger wrote: >>> On Tue, 19 Dec 2017 11:42:33 -0800 >>> "Samudrala, Sridhar" wrote: >>> >>>> On 12/19/2017 10:41 AM, Stephen Hemminger wrote: >>>>> On Tue, 19 Dec 2017 13:21:17 -0500 (EST) >>>>> David Miller wrote: >>>>> >>>>>> From: Stephen Hemminger >>>>>> Date: Tue, 19 Dec 2017 09:55:48 -0800 >>>>>> >>>>>>> could be 10ms, just enough to let udev do its renaming >>>>>> Please, move to some kind of notification or event based handling of >>>>>> this problem. >>>>>> >>>>>> No delay is safe, what if userspace gets swapped out or whatever >>>>>> else might make userspace stall unexpectedly? >>>>>> >>>>> The plan is to remove the delay and do the naming in the kernel. >>>>> This was suggested by Lennart since udev is only doing naming policy >>>>> because kernel names were not repeatable. >>>>> >>>>> This makes the VF show up as "ethN_vf" on Hyper-V which is user friendly. >>>>> >>>>> Patch is pending. >>>> Do we really need to delay the setup until the name is changed? >>>> Can't we call dev_set_mtu() and dev_open() until dev_change_name() is done? >>>> >>>> Thanks >>>> Sridhar >>> You can call dev_set_mtu, but when dev_open is done the device name >>> can not be changed by userspace. >> I did a quick test to remove the delay and also the dev_open() call and >> i don't see >> any issues with virtio taking over the VF datapath. >> Only the netdev_info() messages may show old device name. >> >> Any specific scenario where we need to explicitly call  VF's dev_open() >> in the VF setup process? >> I tried i40evf driver loaded after virtio_net  AND  virtio_net loading >> after i40evf. >> > It happens with hotplug. It is possible on Hyper-V to hotplug SR-IOV on > and off while guest is running. If SR-IOV is disabled in host then the > VF device is removed (hotplug) and the inverse. If the master device is > up then the VF device should be brought up by the master device. Even with KVM, we need to hot unplug SR-IOV device on the source host and  plug it back on the destination host to enable live migration. It all works for me even without the dev_open() of the lower device  from the VF setup routine. Will send out a v2 version of this patch without the delayed VF setup after some more testing next week. Thanks Sridhar