Re: [Qemu-devel] [RFC] vhost-user: introduce F_NEED_ALL_IOTLB protocol feature

[Jason Wang <jasowang@redhat.com>]

On 2018年04月11日 15:20, Tiwei Bie wrote:
> This patch introduces VHOST_USER_PROTOCOL_F_NEED_ALL_IOTLB
> feature for vhost-user. By default, vhost-user backend needs
> to query the IOTLBs from QEMU after meeting unknown IOVAs.
> With this protocol feature negotiated, QEMU will provide all
> the IOTLBs to vhost-user backend without waiting for the
> queries from backend. This is helpful when using a hardware
> accelerator which is not able to handle unknown IOVAs at the
> vhost-user backend.
>
> Signed-off-by: Tiwei Bie<tiwei.bie@intel.com>
> ---
> The idea of this patch is to let QEMU push all the IOTLBs
> to vhost-user backend without waiting for the queries from
> the backend. Because hardware accelerator at the vhost-user
> backend may not be able to handle unknown IOVAs.
>
> This is just a RFC for now. It seems that, it doesn't work
> as expected when guest is using kernel driver (To handle
> this case, it seems that some RAM regions' events also need
> to be listened). Any comments would be appreciated! Thanks!

Interesting, a quick question is why this is needed? Can we just use 
exist IOTLB update message?

It looks to me at least kernel does not need this.

Thanks