Hi Arnd,

On 16/11/20 9:07 pm, Arnd Bergmann wrote:

On Mon, Nov 16, 2020 at 6:19 AM Kishon Vijay Abraham I [off-list ref] wrote:

quoted

On 12/11/20 6:54 pm, Arnd Bergmann wrote:

quoted

This looks very  promising indeed, I need to read up on the whole
discussion there. I also see your slides at [1]  that help do explain some
of it. I have one fundamental question that I can't figure out from
the description, maybe you can help me here:

How is the configuration managed, taking the EP case as an
example? Your UseCase1 example sounds like the system that owns
the EP hardware is the one that turns the EP into a vhost device,
and creates a vhost-rpmsg device on top, while the RC side would
probe the pci-vhost and then detect a virtio-rpmsg device to talk to.

That's correct. Slide no 9 in [1] should give the layering details.

quoted

Can it also do the opposite, so you end up with e.g. a virtio-net
device on the EP side and vhost-net on the RC?

Unfortunately no. Again referring slide 9 in [1], we only have
vhost-pci-epf on the EP side which only creates a "vhost_dev" to deal
with vhost side of things. For doing the opposite, we'd need to create
virtio-pci-epf for EP side that interacts with core virtio (and also the
corresponding vhost back end on PCI host).

Ok, I see. So I think this is the opposite of drivers/misc/mic and
the bluefield driver were using, so we would probably end up
needing both.

Then again, I guess the NTB driver would give us the functionality
for free, if it shows a symmetric link?

Right, NTB driver would need "pci_dev" on both sides of the link. But
that would also mean we cannot use pci EP framework which actually uses
"pci_epf".

Thanks
Kishon