Re: [Qemu-devel] [PATCH v2 0/6] vhost-user: Specify and implement device IOTLB support

[Jason Wang <jasowang@redhat.com>]

On 2017年05月31日 23:32, Maxime Coquelin wrote:
>>>> [0]:https://gitlab.com/mcoquelin/dpdk-next-virtio/commits/vhost_iotlb_proto_v2 
>>>>
>>>> [1]:https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg00095.html 
>>>>
>>> Overall, this looks good to me. I do think patch 3 isn't a good idea
>>> though, if slave wants something let it request it.
>>>
>>> Need to find out why does vhost in kernel want the used ring iotlb at
>>> start time - especially considering we aren't even guaranteed one entry
>>> covers the whole ring, and invalidates should affect all addresses at
>>> least in theory.
>>>
>>>
>>
>> The reason is probably we want to verify whether or not we could 
>> correctly access used ring in vhost_vq_init_access(). It was there 
>> since vhost_net is introduced. We can think to remove this limitation 
>> maybe.
>
> Even if we remove the limitation on Kernel side, we will still have to
> keep this workaround for compatibility with older kernels. Having done 
> the test, I can confirm it is currently necessary.
>
> Thanks,
> Maxime 

Right, it was probably too late for the change.

Thanks