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

[Scott Wood <scottwood@freescale.com>]

On Wed, 2015-07-08 at 13:49 +1000, Samuel Mendoza-Jonas wrote:
> 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.

It looks like this ended up going into main kexec, which means I get to find 
some way to distinguish book3s from book3e to avoid that rfid.  Yay.

-Scott