From: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Date: Mon, 1 Mar 2010 02:58:09 +0000 (+0000)
Subject: powerpc: Reset kernel stack on cpu online from cede state
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=8dbce53cc249a76e9450708d291fce5a7e29c6a1;p=mv-sheeva.git

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>
---

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index b24b7001ae1..bed9a29ee38 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
 
 /*
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index d1b124e44d7..349e0af9389 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -146,12 +146,11 @@ static void pseries_mach_cpu_die(void)
 		unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
 
 		/*
-		 * NOTE: Calling start_secondary() here for now to
-		 * start new context.
-		 * However, need to do it cleanly by resetting the
-		 * stack pointer.
+		 * Call to start_secondary_resume() will not return.
+		 * Kernel stack will be reset and start_secondary()
+		 * will be called to continue the online operation.
 		 */
-		start_secondary();
+		start_secondary_resume();
 
 	} else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
 
diff --git a/arch/powerpc/platforms/pseries/offline_states.h b/arch/powerpc/platforms/pseries/offline_states.h
index 202d8692c6a..75a6f480d93 100644
--- a/arch/powerpc/platforms/pseries/offline_states.h
+++ b/arch/powerpc/platforms/pseries/offline_states.h
@@ -35,4 +35,5 @@ static inline void set_default_offline_state(int cpu)
 
 extern enum cpu_state_vals get_preferred_offline_state(int cpu);
 extern int start_secondary(void);
+extern void start_secondary_resume(void);
 #endif