Re: [virtio-comment] [PATCH V2] virtio-gpio: add the device specification

["Enrico Weigelt, metux IT consult" <lkml@metux.net>]

On 07.06.21 07:45, Viresh Kumar wrote:
> On 04-06-21, 14:25, Enrico Weigelt, metux IT consult wrote:
> > On 04.06.21 10:09, Viresh Kumar wrote:
> > > +The \field{VIRTIO_GPIO_REQ_GET_DIRECTION} request is initiated by the guest to
> >
> > Instead of "guest" we should call it "device", since virtio is also
> > meant for real hardware devices.
>
> Did you mean to say "driver" instead of "device" here ? The
> Virtio-device is the virtual hardware entity which is presented to the
> guest OS by the host OS. And the software talking to this device at
> the guest is called as the "driver".

Sorry, now I've mixed it up, too :o

The "host" in VM-terms is called "device" here (while the VM host
emulates the device), since the idea of virtio is it allows devices
also being implemented as real hardware (*1). Note that virtio is
actually a stack of multiple layers, eg. virtio device protocols is
separate from the underlying transport (eg. pcie, mmapped, ... *2).

> I have replaced "host" with "device" and "guest" with "driver" at as
> many places as possible. Thanks.

Yes, that seems correct. If we'd be looking from a pure hardware / bus
perspective, we might even call it "host" instead of "driver", but that
probably would totally confuse people looking from the VM
perspective.

--mtx


*1) If it was meant exclusively for VMs only, there had been lots of
    other ways to do that, which might even be more efficient in certain
    use cases.
*2) I'm actually planning some Linux-internal socket- or device-node
    based transport in order to allow separate userland servers for
    virtio-based devices, eg. for getting virgl running with containers.

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287