Subject: [PATCH] Fix CPU hotplug when using the SLB shadow buffer

From: Michael Neuling <[email-masked]>
Date: Thu, 10 Jan 2008 18:11:54 +1100

Before we register the SLB shadow buffer, we need to invalidate the
entries in the buffer otherwise we can end up stale entries from when we
offlined the CPU.

This patch does this invalidate as well as unregistering the buffer with
PHYP before we offline the cpu.  Tested and fixes crashes seen on 970MP
(thanks to tonyb) and POWER5.

Signed-off-by: Michael Neuling <[email-masked]>
---
Updates for comments by mpe.

Also, thanks to Anton for helping find this problem.

 arch/powerpc/mm/slb.c                        |    2 +-
 arch/powerpc/platforms/pseries/hotplug-cpu.c |    2 ++
 arch/powerpc/platforms/pseries/lpar.c        |    3 +++
 include/asm-powerpc/mmu-hash64.h             |    1 +
 4 files changed, 7 insertions(+), 1 deletion(-)

Index: linux-2.6-ozlabs/arch/powerpc/mm/slb.c
===================================================================
--- linux-2.6-ozlabs.orig/arch/powerpc/mm/slb.c
+++ linux-2.6-ozlabs/arch/powerpc/mm/slb.c
@@ -77,7 +77,7 @@ static inline void slb_shadow_update(uns
 	get_slb_shadow()->save_area[entry].esid = mk_esid_data(ea, ssize, entry);
 }
 
-static inline void slb_shadow_clear(unsigned long entry)
+void slb_shadow_clear(unsigned long entry)
 {
 	get_slb_shadow()->save_area[entry].esid = 0;
 }
Index: linux-2.6-ozlabs/arch/powerpc/platforms/pseries/hotplug-cpu.c
===================================================================
--- linux-2.6-ozlabs.orig/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ linux-2.6-ozlabs/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -29,6 +29,7 @@
 #include <asm/vdso_datapage.h>
 #include <asm/pSeries_reconfig.h>
 #include "xics.h"
+#include "plpar_wrappers.h"
 
 /* This version can't take the spinlock, because it never returns */
 static struct rtas_args rtas_stop_self_args = {
@@ -58,6 +59,7 @@ static void pseries_mach_cpu_die(void)
 	local_irq_disable();
 	idle_task_exit();
 	xics_teardown_cpu(0);
+	unregister_slb_shadow(smp_processor_id(), __pa(get_slb_shadow()));
 	rtas_stop_self();
 	/* Should never get here... */
 	BUG();
Index: linux-2.6-ozlabs/arch/powerpc/platforms/pseries/lpar.c
===================================================================
--- linux-2.6-ozlabs.orig/arch/powerpc/platforms/pseries/lpar.c
+++ linux-2.6-ozlabs/arch/powerpc/platforms/pseries/lpar.c
@@ -253,6 +253,7 @@ void vpa_init(int cpu)
 	int hwcpu = get_hard_smp_processor_id(cpu);
 	unsigned long addr;
 	long ret;
+	int i;
 
 	if (cpu_has_feature(CPU_FTR_ALTIVEC))
 		lppaca[cpu].vmxregs_in_use = 1;
@@ -272,6 +273,8 @@ void vpa_init(int cpu)
 	 */
 	addr = __pa(&slb_shadow[cpu]);
 	if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
+		for (i = 0; i < SLB_NUM_BOLTED; i++)
+			slb_shadow_clear(i);
 		ret = register_slb_shadow(hwcpu, addr);
 		if (ret)
 			printk(KERN_ERR
Index: linux-2.6-ozlabs/include/asm-powerpc/mmu-hash64.h
===================================================================
--- linux-2.6-ozlabs.orig/include/asm-powerpc/mmu-hash64.h
+++ linux-2.6-ozlabs/include/asm-powerpc/mmu-hash64.h
@@ -286,6 +286,7 @@ extern void hpte_init_iSeries(void);
 extern void hpte_init_beat(void);
 extern void hpte_init_beat_v3(void);
 
+extern void slb_shadow_clear(unsigned long entry);
 extern void stabs_alloc(void);
 extern void slb_initialize(void);
 extern void slb_flush_and_rebolt(void);