Re: [Qemu-arm] [Qemu-devel] [PATCH v1 2/2] target-arm: Enable EL2 for the A53s and A57s

[Alistair Francis]

On Tue, May 10, 2016 at 1:09 AM, Peter Maydell <address@hidden> wrote:
> On 10 May 2016 at 01:16, Alistair Francis <address@hidden> wrote:
>> It is actually a u-boot problem. I originally just assumed it was a
>> Linux problem, but it happens before u-boot hands off to Linux.
>
> OK, that makes sense. u-boot tends to be a bit lower level and less
> hardware-agnostic. I just wanted to check it wasn't caused by some
> problem in QEMU's EL3 support we could easily fix.
>
>> It appears that u-boot won't work at all with EL3 enabled but EL2
>> disabled. It always moves to EL2 before moving to EL1 and there is no
>> code prepared to handle going from EL3 directly to EL1.
>>
>> Just for the record, I'm specifically talking about what happens in
>> the do_nonsec_virt_switch() function.
>>
>> It looks like there are three options:
>>  1. Add support to u-boot to drop from EL3 to EL1 (I'm assuming this
>> is possible, as not all implementations have EL2)
>>  2. Just wait until QEMU adds EL2 support
>>  3. Allow a QEMU command line option to start in EL1 instead of EL3
>
> I would be OK with any of these three from a QEMU perspective.
> Fixing u-boot is probably conceptually the nicest but I've never
> looked at u-boot internals so it could be simple or painful...

I had a quick look and it didn't look easy to do unfortunately.

Thanks,

Alistair

>
> Edgar, do you have the list of what we're still missing before we
> can turn on EL2?
>
> thanks
> -- PMM
>