From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>,
Maxime Coquelin <maxime.coquelin@redhat.com>,
dev@dpdk.org, qemu-devel@nongnu.org
Subject: Re: [dpdk-dev] [PATCH 1/2] vhost: enable any layout feature
Date: Tue, 27 Sep 2016 11:11:58 +0800 [thread overview]
Message-ID: <20160927031158.GA25823@yliu-dev.sh.intel.com> (raw)
In-Reply-To: <20160926221112-mutt-send-email-mst@kernel.org>
On Mon, Sep 26, 2016 at 10:24:55PM +0300, Michael S. Tsirkin wrote:
> On Mon, Sep 26, 2016 at 11:01:58AM -0700, Stephen Hemminger wrote:
> > I assume that if using Version 1 that the bit will be ignored
Yes, but I will just quote what you just said: what if the guest
virtio device is a legacy device? I also gave my reasons in another
email why I consistently set this flag:
- we have to return all features we support to the guest.
We don't know the guest is a modern or legacy device. That means
we should claim we support both: VERSION_1 and ANY_LAYOUT.
Assume guest is a legacy device and we just set VERSION_1 (the current
case), ANY_LAYOUT will never be negotiated.
- I'm following the way Linux kernel takes: it also set both features.
Maybe, we could unset ANY_LAYOUT when VERSION_1 is _negotiated_?
The unset after negotiation I proposed turned out it won't work: the
feature is already negotiated; unsetting it only in vhost side doesn't
change anything. Besides, it may break the migration as Michael stated
below.
> Therein lies a problem. If dpdk tweaks flags, updating it
> will break guest migration.
>
> One way is to require that users specify all flags fully when
> creating the virtio net device.
Like how? By a new command line option? And user has to type
all those features?
> QEMU could verify that all required
> flags are set, and fail init if not.
>
> This has other advantages, e.g. it adds ability to
> init device without waiting for dpdk to connect.
>
> However, enabling each new feature would now require
> management work. How about dpdk ships the list
> of supported features instead?
> Management tools could read them on source and destination
> and select features supported on both sides.
That means the management tool would somehow has a dependency on
DPDK project, which I have no objection at all. But, is that
a good idea?
BTW, I'm not quite sure I followed your idea. I mean, how it supposed
to fix the ANY_LAYOUT issue here? How this flag will be set for
legacy device?
--yliu
next prev parent reply other threads:[~2016-09-27 3:11 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-26 6:40 [dpdk-dev] [PATCH 0/2] enables vhost/virtio " Yuanhan Liu
2016-09-26 6:40 ` [dpdk-dev] [PATCH 1/2] vhost: enable " Yuanhan Liu
2016-09-26 18:01 ` Stephen Hemminger
2016-09-26 19:24 ` Michael S. Tsirkin
2016-09-27 3:11 ` Yuanhan Liu [this message]
2016-09-27 19:48 ` Stephen Hemminger
2016-09-27 19:56 ` Michael S. Tsirkin
2016-09-28 2:28 ` Yuanhan Liu
2016-09-29 15:30 ` [dpdk-dev] [Qemu-devel] " Maxime Coquelin
2016-09-29 17:57 ` Michael S. Tsirkin
2016-09-29 20:05 ` Maxime Coquelin
2016-09-29 20:21 ` Michael S. Tsirkin
2016-09-29 21:23 ` Maxime Coquelin
2016-09-30 12:05 ` Maxime Coquelin
2016-09-30 19:16 ` Michael S. Tsirkin
2016-10-10 4:05 ` Yuanhan Liu
2016-10-10 4:17 ` Michael S. Tsirkin
2016-10-10 4:22 ` Yuanhan Liu
2016-10-10 4:25 ` Michael S. Tsirkin
2016-10-10 12:40 ` Maxime Coquelin
2016-10-10 14:42 ` Yuanhan Liu
2016-10-10 14:54 ` Maxime Coquelin
2016-10-11 6:04 ` Yuanhan Liu
2016-10-11 6:39 ` Maxime Coquelin
2016-10-11 6:49 ` Yuanhan Liu
2016-10-03 14:20 ` Maxime Coquelin
2016-10-10 3:37 ` Yuanhan Liu
2016-10-10 3:46 ` Michael S. Tsirkin
2016-10-10 3:59 ` Yuanhan Liu
2016-10-10 4:16 ` Wang, Zhihong
2016-10-10 4:24 ` Michael S. Tsirkin
2016-10-10 4:39 ` Michael S. Tsirkin
2016-10-11 6:57 ` Yuanhan Liu
2016-10-12 3:21 ` Yuanhan Liu
[not found] ` <F5DF4F0E3AFEF648ADC1C3C33AD4DBF16C2409EB@SHSMSX101.ccr.corp.intel.com>
2016-10-13 2:52 ` Yang, Zhiyong
2016-10-10 3:50 ` Yuanhan Liu
2016-10-09 23:20 ` [dpdk-dev] " Michael S. Tsirkin
2016-10-10 3:03 ` Yuanhan Liu
2016-10-10 3:04 ` Michael S. Tsirkin
2016-10-10 3:10 ` Yuanhan Liu
2016-09-26 6:40 ` [dpdk-dev] [PATCH 2/2] net/virtio: " Yuanhan Liu
2016-09-26 18:04 ` Stephen Hemminger
2016-09-29 18:00 ` Michael S. Tsirkin
2016-09-29 18:01 ` Michael S. Tsirkin
2016-11-10 15:18 ` [dpdk-dev] [PATCH 0/2] enables vhost/virtio " Michael S. Tsirkin
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