Re: QEMU features useful for Xen development?

[Alex Bennée <alex.bennee@xxxxxxxxxx>]

Ayan Kumar Halder <ayankuma@xxxxxxx> writes:

> Hi Peter/Alex,
>
> Appreciate your help. :)
>
> On 31/08/2023 11:03, Peter Maydell wrote:
>> On Thu, 31 Aug 2023 at 10:53, Alex Bennée <alex.bennee@xxxxxxxxxx> wrote:
>>>
>>> Peter Maydell <peter.maydell@xxxxxxxxxx> writes:
>>>
>>>> On Thu, 31 Aug 2023 at 01:57, Stefano Stabellini <sstabellini@xxxxxxxxxx> 
>>>> wrote:
>>>>> As Xen is gaining R52 and R82 support, it would be great to be able to
>>>>> use QEMU for development and testing there as well, but I don't think
>>>>> QEMU can emulate EL2 properly for the Cortex-R architecture. We would
>>>>> need EL2 support in the GIC/timer for R52/R82 as well.
>>>> We do actually have a Cortex-R52 model which at least in theory
>>>> should include EL2 support, though as usual with newer QEMU
>>>> stuff it quite likely has lurking bugs; I'm not sure how much
>>>> testing it's had. Also there is currently no board model which
>>>> will work with the Cortex-R52 so it's a bit tricky to use in practice.
>>>> (What sort of board model would Xen want to use it with?)
>>> We already model a bunch of the mps2/mps3 images so I'm assuming adding
>>> the mps3-an536 would be a fairly simple step to do (mps2tz.c is mostly
>>> tweaking config values). The question is would it be a useful target for
>>> Xen?
>> All our MPS2/MPS3 boards are M-profile. That means we have the
>> device models for all the interesting devices on the board, but
>> it would be simpler to write the an536 board model separately.
>> (In particular, the M-profile boards are wrappers around an
>> "ARMSSE" sort-of-like-an-SoC component; there's no equivalent
>> for the Cortex-R52.)
>>
>>>    https://developer.arm.com/documentation/dai0536/latest/
>
> Yes, it will be helpful if Qemu can model this board. We have a
> downstream port of Xen on R52 (upstreaming is in progress).
>
> So, we can test the Qemu model with Xen.
>
> Also if all works fine, we might consider adding this to the upstream
> Xen CI docker.
>
> Out of curiosity, are you planning to add Qemu R52 SoC support to Zephyr ?

Generally enabling other software platforms is out of scope for the QEMU
team as we have plenty enough to do in QEMU itself. However its
certainly useful to have images we can test with.

Eyeballing the Zephyr docs it looks like it already supports some
R-profile cores on various boards, including CPU_CORTEX_R52 for the
NXPS32Z/E board. The BSP sections mostly look like config fragments but
I'm not really familiar with how Zephyr goes together.

I can ask our micro-controller experts what might be missing and need
implementing but I can't commit them to work on it ;-)

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro