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

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 <redacted>
---
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
 
 . = KERNEL_ADDR_OFFSET
 kernel_addr:

-- 
2.4.5

On Wed, 2015-07-08 at 13:29 +1000, Samuel Mendoza-Jonas wrote:

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

On 08/07/15 13:37, Scott Wood wrote:

On Wed, 2015-07-08 at 13:29 +1000, Samuel Mendoza-Jonas wrote:

quoted

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 <redacted>
---
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.

-- 
-----------
LTC Ozlabs
IBM

Hi Scott,

Is kexec-lite meant to be specific to book3s-64? 

It was originally built to test book3s-64 kexec. Likely some other
issues need fixing for other ppc sub arches, but it is nice to
have a very simple kexec.

Anton

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

On 08/07/15 13:37, Scott Wood wrote:

quoted

On Wed, 2015-07-08 at 13:29 +1000, Samuel Mendoza-Jonas wrote:

quoted

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 <redacted>
---
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