powerpc: Rework pseries machine check handler

Rework pseries machine check handler:

- If MSR_RI isn't set, we cannot recover even if the machine check was fully
  recovered

- Rename nonfatal to recovered

- Handle RTAS_DISP_LIMITED_RECOVERY

- Use BUS_MCEERR_AR instead of BUS_ADRERR

- Don't check all the RTAS error log fields when receiving a synchronous
  machine check. Recent versions of the pseries firmware do not fill them
  in during a machine check and instead send a follow up error log with
  the detailed information. If we see a synchronous machine check, and we
  came from userspace then kill the task.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 30 insertions, 18 deletions

diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index 048e25711c6b..d194150cf342 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -259,31 +259,43 @@ int pSeries_system_reset_exception(struct pt_regs *regs)
  * Return 1 if corrected (or delivered a signal).
  * Return 0 if there is nothing we can do.
  */
-static int recover_mce(struct pt_regs *regs, struct rtas_error_log * err)
+static int recover_mce(struct pt_regs *regs, struct rtas_error_log *err)
 {
-        int nonfatal = 0;
+        int recovered = 0;
 
-        if (err->disposition == RTAS_DISP_FULLY_RECOVERED) {
+        if (!(regs->msr & MSR_RI)) {
+                /* If MSR_RI isn't set, we cannot recover */
+                recovered = 0;
+
+        } else if (err->disposition == RTAS_DISP_FULLY_RECOVERED) {
                 /* Platform corrected itself */
-                nonfatal = 1;
-        } else if ((regs->msr & MSR_RI) &&
-                   user_mode(regs) &&
-                   err->severity == RTAS_SEVERITY_ERROR_SYNC &&
-                   err->disposition == RTAS_DISP_NOT_RECOVERED &&
-                   err->target == RTAS_TARGET_MEMORY &&
-                   err->type == RTAS_TYPE_ECC_UNCORR &&
-                   !(current->pid == 0 || is_global_init(current))) {
-                /* Kill off a user process with an ECC error */
-                printk(KERN_ERR "MCE: uncorrectable ecc error for pid %d\n",
-                       current->pid);
-                /* XXX something better for ECC error? */
-                _exception(SIGBUS, regs, BUS_ADRERR, regs->nip);
-                nonfatal = 1;
+                recovered = 1;
+
+        } else if (err->disposition == RTAS_DISP_LIMITED_RECOVERY) {
+                /* Platform corrected itself but could be degraded */
+                printk(KERN_ERR "MCE: limited recovery, system may "
+                       "be degraded\n");
+                recovered = 1;
+
+        } else if (user_mode(regs) && !is_global_init(current) &&
+                   err->severity == RTAS_SEVERITY_ERROR_SYNC) {
+
+                /*
+                 * If we received a synchronous error when in userspace
+                 * kill the task. Firmware may report details of the fail
+                 * asynchronously, so we can't rely on the target and type
+                 * fields being valid here.
+                 */
+                printk(KERN_ERR "MCE: uncorrectable error, killing task "
+                       "%s:%d\n", current->comm, current->pid);
+
+                _exception(SIGBUS, regs, BUS_MCEERR_AR, regs->nip);
+                recovered = 1;
         }
 
         log_error((char *)err, ERR_TYPE_RTAS_LOG, 0);
 
-        return nonfatal;
+        return recovered;
 }
 
 /*