[PATCH 1/2] powerpc/64: Set up a kernel stack for secondaries before cpu_restore()

[Jordan Niethe]

Currently in generic_secondary_smp_init(), cur_cpu_spec->cpu_restore()
is called before a stack has been set up in r1. This was previously fine
as the cpu_restore() functions were implemented in assembly and did not
use a stack. However commit 5a61ef74f269 ("powerpc/64s: Support new
device tree binding for discovering CPU features") used
__restore_cpu_cpufeatures() as the cpu_restore() function for a
device-tree features based cputable entry.  This is a nonleaf C function
and hence requires a stack in r1.

Create the temp kernel stack before calling cpu_restore().

Fixes: 5a61ef74f269 ("powerpc/64s: Support new device tree binding for discovering CPU features")
Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
---
 arch/powerpc/kernel/head_64.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 0e05a9a47a4b..4b7f4c6c2600 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -420,6 +420,10 @@ generic_secondary_common_init:
 	/* From now on, r24 is expected to be logical cpuid */
 	mr	r24,r5
 
+	/* Create a temp kernel stack for use before relocation is on.	*/
+	ld	r1,PACAEMERGSP(r13)
+	subi	r1,r1,STACK_FRAME_OVERHEAD
+
 	/* See if we need to call a cpu state restore handler */
 	LOAD_REG_ADDR(r23, cur_cpu_spec)
 	ld	r23,0(r23)
@@ -448,10 +452,6 @@ generic_secondary_common_init:
 	sync				/* order paca.run and cur_cpu_spec */
 	isync				/* In case code patching happened */
 
-	/* Create a temp kernel stack for use before relocation is on.	*/
-	ld	r1,PACAEMERGSP(r13)
-	subi	r1,r1,STACK_FRAME_OVERHEAD
-
 	b	__secondary_start
 #endif /* SMP */
 
-- 
2.17.1