powerpc: Reset kernel stack on cpu online from cede state

Cpu hotplug (offline) without dlpar operation will place cpu
in cede state and the extended_cede_processor() function will
return when resumed.

Kernel stack pointer needs to be reset before
start_secondary() is called to continue the online operation.

Added new function start_secondary_resume() to do the above
steps.

Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index b24b7001ae19..bed9a29ee383 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -617,6 +617,17 @@ _GLOBAL(start_secondary_prolog)
         std     r3,0(r1)                /* Zero the stack frame pointer */
         bl      .start_secondary
         b       .
+/*
+ * Reset stack pointer and call start_secondary
+ * to continue with online operation when woken up
+ * from cede in cpu offline.
+ */
+_GLOBAL(start_secondary_resume)
+        ld      r1,PACAKSAVE(r13)       /* Reload kernel stack pointer */
+        li      r3,0
+        std     r3,0(r1)                /* Zero the stack frame pointer */
+        bl      .start_secondary
+        b       .
 #endif
 
 /*