[dpdk-dev] [PATCH v8 3/8] vhost: vring queue setup for multiple queue support

Xie, Huawei huawei.xie at intel.com
Tue Oct 27 11:41:23 CET 2015


On 10/27/2015 5:56 PM, Michael S. Tsirkin wrote:
> On Tue, Oct 27, 2015 at 10:51:14AM +0100, Thomas Monjalon wrote:
>> 2015-10-27 11:42, Michael S. Tsirkin:
>>> On Tue, Oct 27, 2015 at 05:30:41PM +0800, Yuanhan Liu wrote:
>>>> On Tue, Oct 27, 2015 at 11:17:16AM +0200, Michael S. Tsirkin wrote:
>>>>> Looking at that, at least when MQ is enabled, please don't key
>>>>> stopping queues off GET_VRING_BASE.
>>>> Yes, that's only a workaround. I guess it has been there for quite a
>>>> while, maybe at the time qemu doesn't send RESET_OWNER message.
>>> RESET_OWNER was a bad idea since it basically closes
>>> everything.
>>>
>>>>> There are ENABLE/DISABLE messages for that.
>>>> That's something new,
>>> That's part of multiqueue support. If you ignore them,
>>> nothing works properly.
>>>
>>>> though I have plan to use them instead, we still
>>>> need to make sure our code work with old qemu, without ENABLE/DISABLE
>>>> messages.
>>> OK but don't rely on this for new code.
>>>
>>>> And I will think more while enabling live migration: I should have
>>>> more time to address issues like this at that time.
>>>>
>>>>> Generally guys, don't take whatever QEMU happens to do for
>>>>> granted! Look at the protocol spec under doc/specs directory,
>>>>> if you are making more assumptions you must document them!
>>>> Indeed. And we will try to address them bit by bit in future.
>>>>
>>>> 	--yliu
>>> But don't pile up these workarounds meanwhile.  I'm very worried.  The
>>> way you are carrying on, each new QEMU is likely to break your
>>> assumptions.
>> I think it may be saner to increase the minimum QEMU version supported in
>> each DPDK release, dropping old stuff progressively.
>> Michael, you are welcome to suggest how to move precisely.
>> Thanks
> This doesn't work for downstreams which need to backport fixes and
> features.
>
> Just go by the spec, and if you find issues, fix them at the
> source instead of working around them - the code is open.
>
> For new features, we have protocol feature bits.
To me, one requirement is we need clear message(or spec) to know when
virtio device (or better queue granularity) could be processed or should
be stopped from processing. We need have a clear state machine in mind.
For another requirement, we hope QEMU could send vhost an ID to let
vhost-user have the ability to identify the connection. Let us discuss
this in other thread.




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