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 <sva...@linux.vnet.ibm.com>
Cc: Gautham R Shenoy <e...@in.ibm.com>
---
arch/powerpc/kernel/head_64.S | 11 +++++++++++
arch/powerpc/platforms/pseries/hotplug-cpu.c | 9 ++++-----
arch/powerpc/platforms/pseries/offline_states.h | 2 +-
3 files changed, 16 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 9258074..567cd57 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -615,6 +615,17 @@ _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 6ea4698..9be7af4 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 22574e0..da07256 100644
--- a/arch/powerpc/platforms/pseries/offline_states.h
+++ b/arch/powerpc/platforms/pseries/offline_states.h
@@ -14,5 +14,5 @@ extern void set_cpu_current_state(int cpu, enum
cpu_state_vals state);
extern enum cpu_state_vals get_preferred_offline_state(int cpu);
extern void set_preferred_offline_state(int cpu, enum cpu_state_vals state);
extern void set_default_offline_state(int cpu);
-extern int start_secondary(void);
+extern void start_secondary_resume(void);
#endif
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