[IA64] Update Altix nofault code

Montecito and Montvale behaves slightly differently than previous
Itanium processors, resulting in the MCA due to a failed PIO read
to sometimes surfacing outside the nofault code.  This code is
based on discussions with Intel CPU architects and verified at
customer sites.

Signed-off-by: Russ Anderson <rja@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/arch/ia64/sn/kernel/xp_nofault.S b/arch/ia64/sn/kernel/xp_nofault.S
index 54e8973b6e99d21679c2083d76c8c0ea2cdfaedf..98e7c7dbfdd84082d5b2adf72d19b6b3309f2762 100644 (file)
--- a/arch/ia64/sn/kernel/xp_nofault.S
+++ b/arch/ia64/sn/kernel/xp_nofault.S
@@ -3,7 +3,7 @@
  * License.  See the file "COPYING" in the main directory of this archive
  * for more details.
  *
- * Copyright (c) 2004-2005 Silicon Graphics, Inc.  All Rights Reserved.
+ * Copyright (c) 2004-2007 Silicon Graphics, Inc.  All Rights Reserved.
  */
 
 
@@ -14,6 +14,11 @@
  * PIO read fails, the MCA handler will force the error to look
  * corrected and vector to the xp_error_PIOR which will return an error.
  *
+ * The definition of "consumption" and the time it takes for an MCA
+ * to surface is processor implementation specific.  This code
+ * is sufficient on Itanium through the Montvale processor family.
+ * It may need to be adjusted for future processor implementations.
+ *
  *     extern int xp_nofault_PIOR(void *remote_register);
  */
 
@@ -22,11 +27,10 @@ xp_nofault_PIOR:
        mov     r8=r0                   // Stage a success return value
        ld8.acq r9=[r32];;              // PIO Read the specified register
        adds    r9=1,r9;;               // Add to force consumption
-       or      r9=r9,r9;;              // Or to force consumption
+       srlz.i;;                        // Allow time for MCA to surface
        br.ret.sptk.many b0;;           // Return success
 
        .global xp_error_PIOR
 xp_error_PIOR:
        mov     r8=1                    // Return value of 1
        br.ret.sptk.many b0;;           // Return failure
-