Re: [PATCH V3 2/4] misc: vop: do not allocate and reassign the used ring

[Vincent Whitchurch]

On Wed, Oct 28, 2020 at 04:50:36PM +0100, Arnd Bergmann wrote:
> I think we should try to do something on top of the PCIe endpoint subsystem
> to make it work across arbitrary combinations of host and device
> implementations,
> and provide a superset of what the MIC driver, (out-of-tree) Bluefield endpoint
> driver, and the NTB subsystem as well as a couple of others used to do,
> each of them tunneling block/network/serial/... over a PCIe link of some
> sort, usually with virtio.

VOP is not PCIe-specific (as demonstrated by the vop-loopback patches I
posted a while ago [1]), and it would be a shame for a replacement to be
tied to the PCIe endpoint subsystem.  There are many SOCs out there
which have multiple Linux-capable processors without cache-coherency
between them.  VOP is (or should I say was since I guess it's being
deleted) the closest we have in mainline to easily get generic virtio
(and not just rpmsg) running between these kind of Linux instances.  If
a new replacement framework were to be PCIe-exclusive then we'd have to
invent one more framework for non-PCIe links to do pretty much the same
thing.

[1] https://lore.kernel.org/lkml/20190403104746.16063-1-vincent.whitchurch@xxxxxxxx/