Re: [kexec-lite PATCH V2] trampoline: Reset primary cpu endian to big-endian

[Samuel Mendoza-Jonas <sam.mj@au1.ibm.com>]

On 08/07/15 13:37, Scott Wood wrote:
> On Wed, 2015-07-08 at 13:29 +1000, Samuel Mendoza-Jonas wrote:
>> Older big-endian ppc64 kernels don't include the FIXUP_ENDIAN check,
>> meaning if we kexec from a little-endian kernel the target kernel will
>> fail to boot.
>> Returning to big-endian before we enter the target kernel ensures that
>> the target kernel can boot whether or not it includes FIXUP_ENDIAN.
>>
>> Signed-off-by: Samuel Mendoza-Jonas <sam.mj@au1.ibm.com>
>> ---
>> V2: As suggested by Anton take advantage of the rfid call and switch off
>> MSR_LE and branch to the target kernel in the same step.
>>
>>  kexec_trampoline.S | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/kexec_trampoline.S b/kexec_trampoline.S
>> index a3eb314..3751112 100644
>> --- a/kexec_trampoline.S
>> +++ b/kexec_trampoline.S
>> @@ -88,8 +88,15 @@ start:
>>  
>>       li      r5,0
>>  
>> -     mtctr   r4
>> -     bctr
>> +     mtsrr0  r4
>> +
>> +     mfmsr   r5
>> +     clrrdi  r5,r5,1         /* Clear MSR_LE */
>> +     mtsrr1  r5
>> +
>> +     li      r5,0
>> +
>> +     rfid
> 
> Is kexec-lite meant to be specific to book3s-64?  The README just says "A 
> simple kexec for flattened device tree platforms" and I see a __powerpc64__ 
> ifdef in kexec_trampoline.S (but not in the above patch)...
> 
> -Scott
> 

I believe that particular ifdef is to check if we're little-endian when reading
the device tree, but that's still a good point - I'll check with Anton.

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