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

From: Scott Wood <[email-masked]>
Date: Tue, 7 Jul 2015 22:37:16 -0500

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 <[email-masked]>
> ---
> 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