Re: [Stratos-dev] Enabling hypervisor agnosticism for VirtIO backends

[Alex Bennée <alex.bennee@xxxxxxxxxx>]

AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> writes:

> Hi François,
>
> On Thu, Aug 12, 2021 at 09:55:52AM +0200, Fran??ois Ozog wrote:
>> I top post as I find it difficult to identify where to make the comments.
>
> Thank you for the posting. 
> I think that we should first discuss more about the goal/requirements/
> practical use cases for the framework.
>
>> 1) BE acceleration
>> Network and storage backends may actually be executed in SmartNICs. As
>> virtio 1.1 is hardware friendly, there may be SmartNICs with virtio 1.1 PCI
>> VFs. Is it a valid use case for the generic BE framework to be used in this
>> context?
>> DPDK is used in some BE to significantly accelerate switching. DPDK is also
>> used sometimes in guests. In that case, there are no event injection but
>> just high performance memory scheme. Is this considered as a use case?
>
> I'm not quite familiar with DPDK but it seems to be heavily reliant
> on not only virtqueues but also kvm/linux features/functionality, say,
> according to [1].
> I'm afraid that DPDK is not suitable for primary (at least, initial)
> target use.
> # In my proposal, virtio-proxy, I have in mind the assumption that we would
> # create BE VM as a baremetal application on RTOS (and/or unikernel.)
>
> But as far as virtqueue is concerned, I think we can discuss in general
> technical details as Alex suggested, including:
> - sharing or mapping memory regions for data payload
> - efficient notification mechanism
>
> [1] https://www.redhat.com/en/blog/journey-vhost-users-realm
>
>> 2) Virtio as OS HAL
>> Panasonic CTO has been calling for a virtio based HAL and based on the
>> teachings of Google GKI, an internal HAL seem inevitable in the long term.
>> Virtio is then a contender to Google promoted Android HAL. Could the
>> framework be used in that context?
>
> In this case, where will the implementation of "HAL" reside?
> I don't think the portability of "HAL" code (as a set of virtio BEs)
> is a requirement here.

When I hear people referring to VirtIO HALs I'm thinking mainly of
VirtIO FE's living in a Linux kernel. There are certainly more devices
that can get added but the commonality on the guest side I think is
pretty much a solved problem (modulo Linux-ism's creeping into the
virtio spec).

-- 
Alex Bennée