On Fri, Feb 14, 2020 at 11:23:27AM +0800, Jason Wang wrote:
Certainly yes, something creating many char devs should have aThough all vDPA devices have the same programming interface, but theHere we are talking about the /dev/XX node that provides the
semantic is different. So it looks to me that use bus complies what
Each device class defines a set of semantics and a programming interface
that devices of that class adhere to. Device drivers are the
implementation of that programming interface for a particular device on
a particular bus.
I'm confused here, are you suggesting to use class to create char device in
vhost-vdpa? That's fine but the comment should go for vhost-vdpa patch.
class. That makes the sysfs work as expected
I suppose this is vhost user?
I admit I don't really see how this
vhost stuff works, all I see are global misc devices? Very unusual for
a new subsystem to be using global misc devices..
I would have expected that a single VDPA device comes out as a single
char dev linked to only that VDPA device.
Okay, this is fine, but why do you need two busses to accomplish this?All the vdpa devices have the same basicThat's not true, char interface is only used for vhost. Kernel virtio driver
chardev interface and discover any semantic variations 'in band'
does not need char dev but a device on the virtio bus.
Shouldn't the 'struct virito_device' be the plug in point for HW
drivers I was talking about - and from there a vhost-user can connect
to the struct virtio_device to give it a char dev or a kernel driver
can connect to link it to another subsystem?
It is easy to see something is going wrong with this design because
the drivers/virtio/virtio_vdpa.c mainly contains a bunch of trampoline
functions reflecting identical calls from one ops struct to a
different ops struct.
This suggests the 'vdpa' is some subclass of
'virtio' and it is possibly better to model it by extending 'struct
virito_device' to include the vdpa specific stuff.
Where does the vhost-user char dev get invovled in with the v2 series?
Is that included?
No.Every class of virtio traffic is going to need a special HW driver toAre you saying, e.g it's the charge of IFCVF driver to create vhost char dev
enable VDPA, that special driver can create the correct vhost side
and other stuffs?