Re: [Qemu-devel] [RFC v1 2/2] arm: boot: Add EL jump-down code for Linux

[Peter Maydell]

On 1 September 2014 23:41, Peter Crosthwaite
<address@hidden> wrote:
> On Tue, Sep 2, 2014 at 3:15 AM, Peter Maydell <address@hidden> wrote:
>> On 19 August 2014 01:54, Peter Crosthwaite <address@hidden> wrote:
>>> Linux should boot in EL2 or EL1. If in EL3, jump down before handing
>>> off to Linux.
>>>
>>> Signed-off-by: Peter Crosthwaite <address@hidden>
>>
>> The other way we could do this would be to have the
>> do_cpu_reset() hook put the CPU into EL2 or EL1 before
>> starting the boot code. (This would be in line with how it
>> would work for KVM).
>>
>
> Tried that at first, and the problem we found was it introduced a
> reset order dep. The arm-boot and CPU race on who sets the EL.

Surely there's already a reset order dependency, because
both the arm-boot reset hook and CPU reset proper want
to initialise the PC ?

>> Have you thought about how this would work for
>> secondary CPUs (which boot via PSCI poweron)?

> Not yet although I expect something similar.

Hmm. I guess PSCI poweron won't even go through
the boot.c code, thinking a bit more about it. I need to
look at the TCG PSCI patches too.

-- PMM