[PATCH v2 5/6] arm: Use armv8_switch_to_el1 env to switch to EL1

[Peter Hoyes]

Hi,

On 03/09/2021 00:49, Tom Rini wrote:
> On Fri, Sep 03, 2021 at 12:07:20AM +0100, Andre Przywara wrote:
>> On Thu, 2 Sep 2021 18:42:05 -0400
>> Tom Rini <trini at konsulko.com> wrote:
>>
>> Hi Tom,
>>
>>> On Thu, Aug 19, 2021 at 04:53:13PM +0100, Peter Hoyes wrote:
>>>
>>>> From: Peter Hoyes <Peter.Hoyes at arm.com>
>>>>
>>>> Use the environment variable armv8_switch_to_el1 to determine whether
>>>> to switch to EL1 at runtime. This is an alternative to the
>>>> CONFIG_ARMV8_SWITCH_TO_EL1 compile-time option.
>>>>
>>>> The environment variable will be ineffective if the ARMV8_MULTIENTRY
>>>> config is used.
>>>>
>>>> This is required by the Armv8r64 architecture, which must be able to
>>>> boot at S-EL1 for Linux but may need to boot at other ELs for other
>>>> systems.
>>>>
>>>> Signed-off-by: Peter Hoyes <Peter.Hoyes at arm.com>
>>> Applied to u-boot/next, thanks!
>> Sorry for keeping silent on this, we had some internal discussions
>> here, and we don't think this is the right approach.
> Well, oops on my part too.
Oops here too.
>
>> This whole CONFIG_ARMV8_SWITCH_TO_EL1 solution is actually already
>> questionable, as it goes somewhat against the PSCI spec, which requires
>> secondaries to enter in the highest non-secure exception level (Section
>> 6.1.3: "... As described in Figure 6, the return Exception level for a
>> CPU_ON call is the highest Non secure Exception level implemented.")
>>
>> In any case the primary core must enter an the same exception level as
>> the secondaries, or all hell breaks loose. The current code violates
>> this bluntly when the dynamic method is used (as the spin table code
>> doesn't know about this variable).
>>
>> So can you please revert this patch? We are looking into a different
> Should I undo just this, or the whole vexpress_aemv8r series?
>
We are still discussing how to support v8-R internally and it'll probably
take a while to resolve.

Please can you revert the wholeseries apart from patch 1, which isn't
actually specific to the v8-R. (If preferable,I can submit a "v3" to
clarify this).

Peter
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