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From: Stephen Hemminger <stephen@networkplumber.org>
To: Gareth Bradshaw <gareth@vectra.ai>
Cc: "users@dpdk.org" <users@dpdk.org>
Subject: Re: [dpdk-users] Hyper-V multi-queue not working on Kernel v4.20
Date: Wed, 5 Dec 2018 08:03:51 -0800	[thread overview]
Message-ID: <20181205080351.10936ea4@xeon-e3> (raw)
In-Reply-To: <BYAPR08MB495117823D47D2D461E3B267C6A80@BYAPR08MB4951.namprd08.prod.outlook.com>

On Wed, 5 Dec 2018 11:05:58 +0000
Gareth Bradshaw <gareth@vectra.ai> wrote:

> Hi,
> 
> I'm developing a DPDK application for Hyper-V and would like to use Kernel v4.20 as it fixes a crash in previous kernels (per this pull request<https://github.com/torvalds/linux/commit/cdfa835c6e5e87d145f9f632b58843de97509f2b>) but multi-queue support seems to have broken in that kernel.  It works in kernels 4.17, 4.18 and 4.19.
> 
> Using testpmd with parameters "--forward-mode=txonly --nb-cores=3 --txq=3 --rxq=3" I get the following error "vmbus_uio_get_subchan(): invalid subchannel id 0".
> 
> Tracing the code a bit I find that it's trying to read /sys/bus/devices/<devid>/channels/21/subchannel_id but when I try to cat the same file I get the error "Invalid argument".  I've compared to previous kernel versions and see the following differences:
> 
>   *   When the VM boots, the device is bound to the kernel driver and there are 4 channels on both kernel versions.  It's a 4 core VM.
>   *   When I bind the device to uio_hv_generic, kernel v.19.5 (and previous) has a single channel and it has a valid subchannel_id.  On kernel 4.20 the 4 channel folders remain but they are all invalid.
>   *   When I start testpmd with 3 queues, on kernel v4.19.5 two additional channels are created, they're valid and testpmd works as expected.  On kernel 4.20 the 4 invalid channels remain invalid and testpmd gives the error I mentioned.
> 
> Any help getting this working would be greatly appreciated.
> 
> Thanks
> Gareth
> 
> 
> 
> 
> 
> 

There is a race that shows up in sub channel initialization, it is being worked on the development
mailing list. No resolution yet.

  reply	other threads:[~2018-12-05 16:03 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-05 11:05 Gareth Bradshaw
2018-12-05 16:03 ` Stephen Hemminger [this message]
2018-12-05 17:10   ` Gareth Bradshaw
2018-12-13 16:48     ` Gareth Bradshaw
2018-12-13 17:47       ` Stephen Hemminger

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