2 files changed, 25 insertions, 2 deletions

diff --git a/arch/ia64/sn/kernel/setup.c b/arch/ia64/sn/kernel/setup.c
index 5b84836c217..8b6d5c84470 100644
--- a/arch/ia64/sn/kernel/setup.c
+++ b/arch/ia64/sn/kernel/setup.c
@@ -3,7 +3,7 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
- * Copyright (C) 1999,2001-2005 Silicon Graphics, Inc. All rights reserved.
+ * Copyright (C) 1999,2001-2006 Silicon Graphics, Inc. All rights reserved.
  */
 
 #include <linux/config.h>
@@ -498,6 +498,7 @@ void __init sn_setup(char **cmdline_p)
          * for sn.
          */
         pm_power_off = ia64_sn_power_down;
+        current->thread.flags |= IA64_THREAD_MIGRATION;
 }
 
 /**
@@ -660,7 +661,8 @@ void __init sn_cpu_init(void)
                         SH2_PIO_WRITE_STATUS_1, SH2_PIO_WRITE_STATUS_3};
                 u64 *pio;
                 pio = is_shub1() ? pio1 : pio2;
-                pda->pio_write_status_addr = (volatile unsigned long *) LOCAL_MMR_ADDR(pio[slice]);
+                pda->pio_write_status_addr =
+                   (volatile unsigned long *)GLOBAL_MMR_ADDR(nasid, pio[slice]);
                 pda->pio_write_status_val = is_shub1() ? SH_PIO_WRITE_STATUS_PENDING_WRITE_COUNT_MASK : 0;
         }
 
diff --git a/arch/ia64/sn/kernel/sn2/sn2_smp.c b/arch/ia64/sn/kernel/sn2/sn2_smp.c
index b2e1e746b47..d9d306c79f2 100644
--- a/arch/ia64/sn/kernel/sn2/sn2_smp.c
+++ b/arch/ia64/sn/kernel/sn2/sn2_smp.c
@@ -93,6 +93,27 @@ static inline unsigned long wait_piowc(void)
         return (ws & SH_PIO_WRITE_STATUS_WRITE_DEADLOCK_MASK) != 0;
 }
 
+/**
+ * sn_migrate - SN-specific task migration actions
+ * @task: Task being migrated to new CPU
+ *
+ * SN2 PIO writes from separate CPUs are not guaranteed to arrive in order.
+ * Context switching user threads which have memory-mapped MMIO may cause
+ * PIOs to issue from seperate CPUs, thus the PIO writes must be drained
+ * from the previous CPU's Shub before execution resumes on the new CPU.
+ */
+void sn_migrate(struct task_struct *task)
+{
+        pda_t *last_pda = pdacpu(task_thread_info(task)->last_cpu);
+        volatile unsigned long *adr = last_pda->pio_write_status_addr;
+        unsigned long val = last_pda->pio_write_status_val;
+
+        /* Drain PIO writes from old CPU's Shub */
+        while (unlikely((*adr & SH_PIO_WRITE_STATUS_PENDING_WRITE_COUNT_MASK)
+                        != val))
+                cpu_relax();
+}
+
 void sn_tlb_migrate_finish(struct mm_struct *mm)
 {
         /* flush_tlb_mm is inefficient if more than 1 users of mm */