[IA64] MCA recovery: kernel context recovery table

Memory errors encountered by user applications may surface
when the CPU is running in kernel context.  The current code
will not attempt recovery if the MCA surfaces in kernel
context (privilage mode 0).  This patch adds a check for cases
where the user initiated the load that surfaces in kernel
interrupt code.

An example is a user process lauching a load from memory
and the data in memory had bad ECC.  Before the bad data
gets to the CPU register, and interrupt comes in.  The
code jumps to the IVT interrupt entry point and begins
execution in kernel context.  The process of saving the
user registers (SAVE_REST) causes the bad data to be loaded
into a CPU register, triggering the MCA.  The MCA surfaces in
kernel context, even though the load was initiated from
user context.

As suggested by David and Tony, this patch uses an exception
table like approach, puting the tagged recovery addresses in
a searchable table.  One difference from the exception table
is that MCAs do not surface in precise places (such as with
a TLB miss), so instead of tagging specific instructions,
address ranges are registers.  A single macro is used to do
the tagging, with the input parameter being the label
of the starting address and the macro being the ending
address.  This limits clutter in the code.

This patch only tags one spot, the interrupt ivt entry.
Testing showed that spot to be a "heavy hitter" with
MCAs surfacing while saving user registers.  Other spots
can be added as needed by adding a single macro.

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

1 files changed, 15 insertions, 7 deletions

diff --git a/arch/ia64/kernel/mca_drv.c b/arch/ia64/kernel/mca_drv.c
index e883d85906db..37c88eb55873 100644
--- a/arch/ia64/kernel/mca_drv.c
+++ b/arch/ia64/kernel/mca_drv.c
@@ -6,6 +6,7 @@
  * Copyright (C) Hidetoshi Seto (seto.hidetoshi@jp.fujitsu.com)
  * Copyright (C) 2005 Silicon Graphics, Inc
  * Copyright (C) 2005 Keith Owens <kaos@sgi.com>
+ * Copyright (C) 2006 Russ Anderson <rja@sgi.com>
  */
 #include <linux/config.h>
 #include <linux/types.h>
@@ -121,11 +122,12 @@ mca_page_isolate(unsigned long paddr)
  */
 
 void
-mca_handler_bh(unsigned long paddr)
+mca_handler_bh(unsigned long paddr, void *iip, unsigned long ipsr)
 {
-        printk(KERN_ERR
-                "OS_MCA: process [pid: %d](%s) encounters MCA (paddr=%lx)\n",
-                current->pid, current->comm, paddr);
+        printk(KERN_ERR "OS_MCA: process [cpu %d, pid: %d, uid: %d, "
+                "iip: %p, psr: 0x%lx,paddr: 0x%lx](%s) encounters MCA.\n",
+                raw_smp_processor_id(), current->pid, current->uid,
+                iip, ipsr, paddr, current->comm);
 
         spin_lock(&mca_bh_lock);
         switch (mca_page_isolate(paddr)) {
@@ -442,21 +444,26 @@ recover_from_read_error(slidx_table_t *slidx,
         if (!peidx_bottom(peidx) || !(peidx_bottom(peidx)->valid.minstate))
                 return 0;
         psr1 =(struct ia64_psr *)&(peidx_minstate_area(peidx)->pmsa_ipsr);
+        psr2 =(struct ia64_psr *)&(peidx_minstate_area(peidx)->pmsa_xpsr);
 
         /*
          *  Check the privilege level of interrupted context.
          *   If it is user-mode, then terminate affected process.
          */
-        if (psr1->cpl != 0) {
+
+        pmsa = sos->pal_min_state;
+        if (psr1->cpl != 0 ||
+           ((psr2->cpl != 0) && mca_recover_range(pmsa->pmsa_iip))) {
                 smei = peidx_bus_check(peidx, 0);
                 if (smei->valid.target_identifier) {
                         /*
                          *  setup for resume to bottom half of MCA,
                          * "mca_handler_bhhook"
                          */
-                        pmsa = sos->pal_min_state;
-                        /* pass to bhhook as 1st argument (gr8) */
+                        /* pass to bhhook as argument (gr8, ...) */
                         pmsa->pmsa_gr[8-1] = smei->target_identifier;
+                        pmsa->pmsa_gr[9-1] = pmsa->pmsa_iip;
+                        pmsa->pmsa_gr[10-1] = pmsa->pmsa_ipsr;
                         /* set interrupted return address (but no use) */
                         pmsa->pmsa_br0 = pmsa->pmsa_iip;
                         /* change resume address to bottom half */
@@ -466,6 +473,7 @@ recover_from_read_error(slidx_table_t *slidx,
                         psr2 = (struct ia64_psr *)&pmsa->pmsa_ipsr;
                         psr2->cpl = 0;
                         psr2->ri  = 0;
+                        psr2->bn  = 1;
                         psr2->i  = 0;
 
                         return 1;