[U-Boot] [PATCH v5 1/2] armv8: Support loading 32-bit OS in AArch32 execution state

[Ryan Harkin]

On 7 July 2016 at 13:30, Alexander Graf <agraf at suse.de> wrote:
> On 07/07/2016 02:16 PM, Ryan Harkin wrote:
>>
>> On 7 July 2016 at 07:30, Alison Wang <b18965 at freescale.com> wrote:
>>>
>>> To support loading a 32-bit OS, the execution state will change from
>>> AArch64 to AArch32 when jumping to kernel.
>>>
>>> The architecture information will be got through checking FIT image,
>>> then U-Boot will load 32-bit OS or 64-bit OS automatically.
>>>
>>> Signed-off-by: Ebony Zhu <ebony.zhu at nxp.com>
>>> Signed-off-by: Alison Wang <alison.wang at nxp.com>
>>> Signed-off-by: Chenhui Zhao <chenhui.zhao at nxp.com>
>>
>> Unfortunately, this patch fails to boot for me.
>>
>> On FVP Foundation models, I see this error before the model hangs:
>>
>> [snip]
>> Starting kernel ...
>>
>> resetting ...
>> [snip]
>>
>> And I see the same output on AEMv8 Base models and Juno boards, only
>> they reset continuously rather than hang.
>>
>> I think the problem is that I see this from ARM Trusted Firmware on boot:
>>
>> INFO:    BL31: Preparing for EL3 exit to normal world
>>
>> Looking at the patch, it appears to be changing everything to boot in EL2.
>
>
> That was the case before the patch (with the removal of the EL1 boot thing)
> already. Linux can't run in EL3, that's why it has to boot in EL2 (or EL1,
> but that really should be limited to VMs).
>

Pah!  I misread the patch, specifically this hunk (and the one before
it, I suppose):

diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
index e3c9832..59adab8 100644
--- a/arch/arm/lib/bootm.c
+++ b/arch/arm/lib/bootm.c
@@ -193,7 +193,6 @@ static void do_nonsec_virt_switch(void)
 {
     smp_kick_all_cpus();
     dcache_disable();    /* flush cache before swtiching to EL2 */
-    armv8_switch_to_el2();
 }
 #endif

That's a "-", not a "+" on the call to armv8_switch_to_el2().

Either way, all my platforms are dead with this patch.


>
> Alex
>