Re: QEMU features useful for Xen development?

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On Thu, 31 Aug 2023 at 10:53, Alex Bennée <alex.bennee@linaro.org> wrote:
>>
>>
>> Peter Maydell <peter.maydell@linaro.org> writes:
>>
>> > On Thu, 31 Aug 2023 at 01:57, Stefano Stabellini <sstabellini@kernel.org> 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/

It's not super clear from the design notes but it does mention the
SSE-200 sub-system as the basis for peripherals. Specifically the blocks
are:

  Arm Cortex-R52 Processor
  Arm CoreSight SoC-400 (n/a for QEMU)
  Cortex-M System Design Kit
  PL022 Serial Port
  NIC-400 Network interconnect

But if writing it from scratch is simpler so be it. The real question is
what new hardware would we need to model to be able to bring something
up that is useful to Xen?

>> > The Cortex-R82 would be more work, because (unlike the R52) it's
>> > AArch64, and we don't have Armv8-R AArch64 support yet, only the AArch32.
>> >
>> > I haven't looked at whether GIC on R-profile requires any changes
>> > from the A-profile GIC; on A-profile obviously we emulate the
>> > virtualization support already.
>> >

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro