Pull sn2-mmio-writes into release branch

Hand-fixed conflicts:
	include/asm-ia64/machvec_sn2.h

Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --cc arch/ia64/sn/kernel/setup.c
Simple merge

diff --cc arch/ia64/sn/kernel/sn2/sn2_smp.c
index b2e1e74,1b33fd5..d9d306c
--- 1/arch/ia64/sn/kernel/sn2/sn2_smp.c
--- 2/arch/ia64/sn/kernel/sn2/sn2_smp.c
+++ b/arch/ia64/sn/kernel/sn2/sn2_smp.c
@@@ -90,13 -166,33 +90,34 @@@ static inline unsigned long wait_piowc(
        do {
                cpu_relax();
        } while (((ws = *piows) & SH_PIO_WRITE_STATUS_PENDING_WRITE_COUNT_MASK) != zeroval);
 -      return ws;
 +      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)
  {
 -      if (mm == current->mm)
 +      /* flush_tlb_mm is inefficient if more than 1 users of mm */
 +      if (mm == current->mm && mm && atomic_read(&mm->mm_users) == 1)
                flush_tlb_mm(mm);
  }
  

diff --cc include/asm-ia64/machvec_sn2.h
Simple merge

diff --cc include/asm-ia64/processor.h
Simple merge

diff --cc include/asm-ia64/system.h
Simple merge

diff --cc include/asm-ia64/thread_info.h
Simple merge