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Re: [Qemu-devel] [RFC PATCH 4/4] vhost-user: Add new option to specify v
From: |
Tetsuya Mukawa |
Subject: |
Re: [Qemu-devel] [RFC PATCH 4/4] vhost-user: Add new option to specify vhost-user backend supports |
Date: |
Tue, 26 May 2015 13:29:09 +0900 |
User-agent: |
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 2015/05/26 11:46, Tetsuya Mukawa wrote:
> Hi Eric,
>
> On 月, 2015-05-25 at 16:11 -0600, Eric Blake wrote:
>> On 05/25/2015 01:28 AM, Tetsuya Mukawa wrote:
>>> This patch adds 'backend_features' option for vhost-user backends.
>>> If this option is specified, QEMU assumes vhost-user backends support
>>> the features specified by user, and QEMU can start without vhost-user
>>> backend.
>>>
>>> Here are examples.
>>> * QEMU is configured as vhost-user client.
>>> -chardev socket,id=chr0,path=/tmp/sock,reconnect=3 \
>>> -netdev
>>> vhost-user,id=net0,chardev=chr0,vhostforce,backend_features=0x68000 \
>>> -device virtio-net-pci,netdev=net0 \
>>>
>>> * QEMU is configured as vhost-user server.
>>> -chardev socket,id=chr0,path=/tmp/sock,server,nowait \
>>> -netdev
>>> vhost-user,id=net0,chardev=chr0,vhostforce,backend_features=0x68000 \
>>> -device virtio-net-pci,netdev=net0 \
>>>
>>> To know vhost-user backend features that the backend expects, please
>>> specify 0xffffffff as backend_features, then invoke QEMU and check error log
>>> like below.
>>>
>>> Lack of backend features. Expected 0xffffffff, but receives 0x68000
>>>
>>> Above log indicates the backend features QEMU should be passed.
>>>
>>> Signed-off-by: Tetsuya Mukawa <address@hidden>
>>> ---
>>> +++ b/qapi-schema.json
>>> @@ -2243,6 +2243,8 @@
>>> #
>>> # @queues: #optional number of queues to be created for multiqueue capable
>>> tap
>>> #
>>> +# @backend_features: #optional feature flag to support vhost user backend
>> Missing a (since 2.4) designation.
>>
>> New interfaces should prefer - over _, but I see that you are consistent
>> with vnet_hder already in this struct so it is okay.
>>
>>> +#
>>> # Since 1.2
>>> ##
>>> { 'struct': 'NetdevTapOptions',
>>> @@ -2259,7 +2261,8 @@
>>> '*vhostfd': 'str',
>>> '*vhostfds': 'str',
>>> '*vhostforce': 'bool',
>>> - '*queues': 'uint32'} }
>>> + '*queues': 'uint32',
>>> + '*backend_features':'uint64'} }
>> Ewww. Making users figure out what integers to pass is NOT user
>> friendly. Better would be an enum type, and make the parameter an
>> optional array of enum values.
> Thanks for your comments.
> I guess below may be good example. Is this same as your suggestion?
>
> virtio-net-pci,netdev=hostnet3,id=net3,gso=off,guest_tso4=off,guest_tso6=off
>
> So I will improve 'backend-features' like below.
>
> backend-features=gso=off,guest_tso4=off,guest_tso6=off
>
> Also I will fix 'qapi-schema.json' to work like above.
I seems it's impossible to implement like above.
I may need to implement like below.
virtio-net-pci,netdev=hostnet3,id=net3,backend_gso=on,backend_guest_tso4=on,backend_guest_tso6=on
Tetsuya
>>>
>>> ##
>>> # @NetdevSocketOptions
>>> @@ -2444,12 +2447,15 @@
>>> #
>>> # @vhostforce: #optional vhost on for non-MSIX virtio guests (default:
>>> false).
>>> #
>>> +# @backend_features: #optional feature flag to support vhost user backend
>>> (default: 0).
>>> +#
>> Long line. Please wrap to fit within 80 columns. Missing (since 2.4)
>> deisgnation.
> I will fix it in v2 patch.
>
>> Again, I don't like making users know a raw integer; an
>> enum type would be better.
>>
>>> # Since 2.1
>>> ##
>>> { 'struct': 'NetdevVhostUserOptions',
>>> 'data': {
>>> 'chardev': 'str',
>>> - '*vhostforce': 'bool' } }
>>> + '*vhostforce': 'bool',
>>> + '*backend_features': 'uint64' } }
>> This struct has no pre-existing _, so the name 'backend-features' is nicer.
>>
> Also I will fix it.
>
> Regards,
> Tetsuya
>
>
[Qemu-devel] [PATCH v1 0/4] Add feature to start QEMU without vhost-user backend, Tetsuya Mukawa, 2015/05/29