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

From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH v1 2/2] target-arm: Enable EL2 for the A53s and A57s
Date: Tue, 10 May 2016 09:09:55 +0100

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...

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

-- PMM

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