From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: dev@dpdk.org, stable@dpdk.org, Ilya Maximets <i.maximets@samsung.com>
Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH 1/8] net/virtio: revert "virtio: fix restart"
Date: Fri, 4 Nov 2016 22:28:07 +0800 [thread overview]
Message-ID: <20161104142807.GB12283@yliu-dev.sh.intel.com> (raw)
In-Reply-To: <4dec2204-4da9-da61-fbbf-d17748f2f9bc@redhat.com>
On Fri, Nov 04, 2016 at 09:09:22AM +0100, Maxime Coquelin wrote:
>
>
> On 11/04/2016 03:00 AM, Yuanhan Liu wrote:
> >On Thu, Nov 03, 2016 at 09:36:52PM +0100, Maxime Coquelin wrote:
> >>Hi Yuanhan,
> >>
> >>On 11/03/2016 05:09 PM, Yuanhan Liu wrote:
> >>>This reverts commit 9a0615af7746 ("virtio: fix restart"); conflict is
> >>>manually addressed.
> >>>
> >>>Kyle reported an issue with above commit
> >>>
> >>> qemu-kvm: Guest moved used index from 5 to 1
> >>>
> >>>with following steps,
> >>>
> >>> 1) Start my virtio interfaces
> >>> 2) Send some traffic into/out of the interfaces
> >>> 3) Stop the interfaces
> >>> 4) Start the interfaces
> >>> 5) Send some more traffic
> >>>
> >>>And here are some quotes from Kyle's analysis,
> >>>
> >>> Prior to the patch, if an interface were stopped then started, without
> >>> restarting the application, the queues would be left as-is, because
> >>> hw->started would be set to 1. Now, calling stop sets hw->started to 0,
> >>> which means the next call to start will "touch the queues". This is the
> >>> unintended side-effect that causes the problem.
> >>
> >>Maybe a good idea to explain what is the problem the revert aims to fix.
> >
> >It aims to fix the issue, by "not touching the queues" on restart.
> >
> >>It does not seem to be clearly stated in the commit message.
> >
> >I was thinking the quote from Kyle is enough. How about following supplement:
> >
> > We should not touch the queues once the init is done, otherwise, the
> > vring state of virtio PMD driver and vhost-user would be inconsistent,
> > leading some issue like above.
> >
> > Thus this patch is reverted.
> >
> >Better now?
> Yes, this is much clearer from my PoV.
Fixed, and series applied to dpdk-next-virtio.
Thanks for the review!
--yliu
next prev parent reply other threads:[~2016-11-04 14:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1478189400-14606-1-git-send-email-yuanhan.liu@linux.intel.com>
2016-11-03 16:09 ` [dpdk-stable] " Yuanhan Liu
2016-11-03 20:36 ` [dpdk-stable] [dpdk-dev] " Maxime Coquelin
2016-11-04 2:00 ` Yuanhan Liu
2016-11-04 8:09 ` Maxime Coquelin
2016-11-04 14:28 ` Yuanhan Liu [this message]
2016-11-04 8:10 ` Maxime Coquelin
[not found] ` <1478338865-26126-1-git-send-email-yuanhan.liu@linux.intel.com>
2016-11-05 9:40 ` [dpdk-stable] [PATCH v2 01/10] net/virtio: revert fix restart Yuanhan Liu
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