Re: [Xen-devel] Xen PV: Sample new PV driver for buffer sharing between domains

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

Hi,
On 09/27/2018 12:39 PM, Lars Kurth wrote:
> Adding a few people who have recently been working on PV drivers, as 
> well as Julien
> Lars
>
> > On 27 Sep 2018, at 06:44, Omkar Bolla 
> > <omkar.bolla@xxxxxxxxxxxxxxxxxxx 
> > <mailto:omkar.bolla@xxxxxxxxxxxxxxxxxxx>> wrote:
> > Hi,
> >
> > I am using Debian as Domain-0 and Debian as Domain-U on Hikey960 
> > platform(ARMv8) and using Xen-4.8 stable release. Here I want to 
> > create a PV frontend and backend to share memory between Domain-0 and 
> > Domain-U.
> >
> >
> > I used below link to create frontend and backend,
> > https://fnordig.de/2016/12/02/xen-a-backend-frontend-driver-example/
The link above has another link to github [1] with 2 chapters. And it 
looks like you have
already modified the sources ("mydevice" -> "vdevb" at least).
So, what are the sources you are using?

You could probably take a look at the relatively small vkbd frontend 
driver [2]
to get some hints.
> > But I am facing below errors while adding device vdevb to xenstore.
> > Below errors I am getting from xenbus_switch_state().
> > vdevb vdevb-0: failed to write error node for device/vdevb/0 (13 
> > writing new state)
If the sources are known then we would need the full scenario which 
leads to the failure.
Could you please also add some debug logs into every function of the 
driver so we see what
and when happens on both backend and frontend sides?
> > Please suggest me, How to create PV drivers.
I would go with any existing driver in the kernel as an example
> > Thanks,
> > Omkar B
> >
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[1] https://github.com/badboy/xen-split-driver-example
[2] 
https://elixir.bootlin.com/linux/latest/source/drivers/input/misc/xen-kbdfront.c
[3] 
https://github.com/badboy/xen-split-driver-example/blob/master/chapter02/activate.sh
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