Re: [Xen-users] Running Xen on RaspberryPi-3-B

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

Please keep xen-users in CC.

On 7/20/19 4:39 AM, Rajagopal Aravindan wrote:
> Hello Julien,
>
> Appreciate your reply, thanks.
>
>  > Instead I would recommend to look at the new RPI4.
> Sure, will give it a look-in.
>
>  >It contains a GIC and the port should be easier.
> Does that mean Xen won't run straight away and some porting needs to be 
> done ?
I bought one recently but I haven't yet had the chance to see how much 
effort is required to getting Xen running on it.
For some general guidance on porting a new board to Xen, please see [1].

> Again, any directions would be helpful, on where/what to start with.
>
>  > So porting Xen on the RPI 3 is probably going to be quite consequent.
> Sounds like Xen & its guests can be made to run on RPi3, assuming 
> information on BRCM GIC is available on the net.
The RPI 3 does not use the GIC so I am not sure what you found online...

> If yes,
>
>   * Getting Xen to run on RPi3 would be a very good case study for
>     understanding its internals, for Xen beginner like me.
I don't think trying to port Xen on the RPI 3 is a good way to 
understand the internals. It would be best to look at platform that are 
closer to Xen requirements...
>   * Should anyone manage to get it running on RPi3  ...
>       o Would Xen be willing to take it upstream ?
Not really. See below...

>       o Or are there reservations about it, since it may NOT be useful
>         on other hardware and hence not worth maintaining ?
AFAIK, the interrupt controller used by the RPI 3 does not support 
virtualization. So this is quite departure from the minimal requirement 
used by Xen.
There are various way to make it working on Xen:
   1) Emulating the interrupt controller
   2) Use a PV interface as used by x86

In both cases, the work is going to be consequent with very limited 
benefits to other platforms.
Cheers,

[1] 
https://www.slideshare.net/xen_com_mgr/xpds16-porting-xen-on-arm-to-a-new-soc-julien-grall-arm
--
Julien Grall

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