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[Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options |
Date: |
Sat, 27 Feb 2010 21:44:18 +0200 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Fri, Feb 26, 2010 at 09:23:01AM -0600, Anthony Liguori wrote:
> On 02/26/2010 08:51 AM, Michael S. Tsirkin wrote:
>> On Thu, Feb 25, 2010 at 01:47:27PM -0600, Anthony Liguori wrote:
>>
>>> On 02/25/2010 12:28 PM, Michael S. Tsirkin wrote:
>>>
>>>> This adds vhost binary option to tap, to enable vhost net accelerator.
>>>> Default is off for now, we'll be able to make default on long term
>>>> when we know it's stable.
>>>>
>>>> vhostfd option can be used by management, to pass in the fd. Assigning
>>>> vhostfd implies vhost=on.
>>>>
>>>> Signed-off-by: Michael S. Tsirkin<address@hidden>
>>>>
>>>>
>>> Since the thinking these days is that macvtap and tap is pretty much all
>>> we'll ever need for vhost-net, perhaps we should revisit -net vhost vs.
>>> -net tap,vhost=X?
>>>
>>> I think -net vhost,fd=X makes a lot more sense than -net
>>> tap,vhost=on,vhostfd=X.
>>>
>>> Regards,
>>>
>>> Anthony Liguori
>>>
>> We'll have to duplicate all tap options.
>> I think long term we will just make vhost=on the default.
>>
>
> I don't think we can. vhost only works when using KVM
Yes, default to on with KVM.
> and it doesn't
> support all of the features of userspace virtio. Since it's in upstream
> Linux without supporting all of the virtio-net features, it's something
> we're going to have to deal with for a long time.
Speaking of vlan filtering etc? It's just a matter of time before it
supports all interesting features. Kernel support is there in net-next
already, userspace should be easy too. I should be able to code it up
once I finish bothering about upstream merge (hint hint :)).
> Furthermore, vhost reduces a virtual machine's security. It offers an
> impressive performance boost (particularly when dealing with 10gbit+
> networking) but for a user that doesn't have such strong networking
> performance requirements, I think it's reasonable for them to not want
> to make a security trade off.
It's hard for me to see how it reduces VM security. If it does, it's
not by design and will be fixed.
> One reason I like -net vhost is that it's a much less obscure syntax and
> it's the sort of thing that is easy to tell users that they should use.
> I understand you're argument for -net tap if you assume vhost=on will
> become the default because that means that users never really have to be
> aware of vhost once it becomes the default. But as I said above, I
> don't think it's reasonable to make it on by default with -net tap.
Not yet, but we'll get there.
>> Users do not really care about vhost, it just makes tap
>> go fater. So promoting it to 1st class options is wrong IMO.
>>
>
> User's should care about vhost because it impacts the features supported
> by the virtual machine and it has security ramifications. It's a great
> feature and I think the most users will want to use it, but I do think
> it's something that users ought to be aware of.
>
> Regards,
>
> Anthony Liguori
- [Qemu-devel] Re: [PATCHv2 09/12] vhost: vhost net support, (continued)
- [Qemu-devel] [PATCHv2 02/12] kvm: add API to set ioeventfd, Michael S. Tsirkin, 2010/02/25
- [Qemu-devel] [PATCHv2 04/12] virtio: add notifier support, Michael S. Tsirkin, 2010/02/25
- [Qemu-devel] [PATCHv2 01/12] tap: add interface to get device fd, Michael S. Tsirkin, 2010/02/25
- [Qemu-devel] [PATCHv2 07/12] virtio: move typedef to qemu-common, Michael S. Tsirkin, 2010/02/25
- [Qemu-devel] [PATCHv2 10/12] tap: add vhost/vhostfd options, Michael S. Tsirkin, 2010/02/25
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Anthony Liguori, 2010/02/25
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Michael S. Tsirkin, 2010/02/26
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Anthony Liguori, 2010/02/26
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options,
Michael S. Tsirkin <=
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Anthony Liguori, 2010/02/28
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Michael S. Tsirkin, 2010/02/28
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Anthony Liguori, 2010/02/28
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Michael S. Tsirkin, 2010/02/28
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Anthony Liguori, 2010/02/28
- [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options, Paul Brook, 2010/02/28
[Qemu-devel] [PATCHv2 11/12] tap: add API to retrieve vhost net header, Michael S. Tsirkin, 2010/02/25
[Qemu-devel] [PATCHv2 06/12] virtio: add set_status callback, Michael S. Tsirkin, 2010/02/25
[Qemu-devel] [PATCHv2 08/12] virtio-pci: fill in notifier support, Michael S. Tsirkin, 2010/02/25