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Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature
From: |
Aaron Conole |
Subject: |
Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature |
Date: |
Fri, 18 Nov 2016 14:21:54 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) |
Maxime Coquelin <address@hidden> writes:
> On 11/18/2016 07:15 PM, Aaron Conole wrote:
>> Maxime Coquelin <address@hidden> writes:
>>
>>> This series implements Virtio spec update from Aaron Conole which
>>> defines a way for the host to expose its max MTU to the guest.
>>>
>>> Changes since RFC v1:
>>> ---------------------
>>> - Rebased on top of v2.8.0-rc0 (2.7.90)
>>> - Write MTU unconditionnaly in netcfg to avoid memory leak (Paolo)
>>> - Add host_mtu property to be able to disable the feature from QEMU
>>>
>>> Maxime Coquelin (3):
>>> vhost-user: Add new protocol feature MTU
>>> vhost-net: Add new MTU feature support
>>> virtio-net: Add MTU feature support
>>>
>>> hw/net/vhost_net.c | 11 +++++++++++
>>> hw/net/virtio-net.c | 14 ++++++++++++++
>>> hw/virtio/vhost-user.c | 11 +++++++++++
>>> include/hw/virtio/vhost.h | 1 +
>>> include/hw/virtio/virtio-net.h | 1 +
>>> include/net/vhost_net.h | 2 ++
>>> 6 files changed, 40 insertions(+)
>>
>> I ran this with a VM, but it seems the offered maximum MTU was of value
>> 0 - is this expected with this version? How can I change the offered
>> value? Sorry, I'm not as familiar with QEMU/libvirt side of the world.
>
> They way I implemented it, the MTU value is to be provided by
> vhost-user process (e.g. OVS/DPDK). I added a Vhost protocol
> feature for this. The sequence is:
> 1. Qemu send VHOST_USER_GET_PROTOCOL_FEATURES request
> 2. DPDK replies with providing supported features
> 3. If DPDK supports VHOST_USER_PROTOCOL_F_MTU, Qemu send
> VHOST_USER_GET_MTU resuest
> 4. DPDK replies with MTU value
>
> Does that make sense?
In the case of a vhost-user backed port, yes (so for instance, if I use
ovs+dpdk vhost-user in client or server mode). However, what about the
non-dpdk case, where I still use a virtio-net driver in kernel and want
to have it backed with, say, a tap device in the host attached to
virbr0 (or some other bridge). It should still pull the mtu from that
device and offer it, I think.
> Another possibility would be that we could directly pass the MTU value
> to Qemu. It may be easier to implement, and to handle migration.
> Problem is that if we do this, this is not the vSwitch that decides the
> MTU to set.
Might be better to determined the mtu by looking at what actually
provides the back-end for the networking.
> Regards,
> Maxime
- Re: [Qemu-devel] [RFC v2 3/3] virtio-net: Add MTU feature support, (continued)
- Re: [Qemu-devel] [RFC v2 3/3] virtio-net: Add MTU feature support, Michael S. Tsirkin, 2016/11/17
- Re: [Qemu-devel] [RFC v2 3/3] virtio-net: Add MTU feature support, Maxime Coquelin, 2016/11/21
- Re: [Qemu-devel] [RFC v2 3/3] virtio-net: Add MTU feature support, Michael S. Tsirkin, 2016/11/21
- Re: [Qemu-devel] [RFC v2 3/3] virtio-net: Add MTU feature support, Maxime Coquelin, 2016/11/22
- Re: [Qemu-devel] [RFC v2 3/3] virtio-net: Add MTU feature support, Michael S. Tsirkin, 2016/11/22
- Re: [Qemu-devel] [RFC v2 3/3] virtio-net: Add MTU feature support, Maxime Coquelin, 2016/11/22
Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Michael S. Tsirkin, 2016/11/17
Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Aaron Conole, 2016/11/18
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Maxime Coquelin, 2016/11/18
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature,
Aaron Conole <=
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Michael S. Tsirkin, 2016/11/21
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Jason Wang, 2016/11/21
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Maxime Coquelin, 2016/11/22
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Aaron Conole, 2016/11/22
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Michael S. Tsirkin, 2016/11/22
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Maxime Coquelin, 2016/11/22
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Michael S. Tsirkin, 2016/11/22
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Jason Wang, 2016/11/22
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Michael S. Tsirkin, 2016/11/22
- Re: [Qemu-devel] [RFC v2 0/3] virtio-net: Add support to MTU feature, Aaron Conole, 2016/11/23