powerpc/powernv: Machine check exception handling.

Add basic error handling in machine check exception handler.

- If MSR_RI isn't set, we can not recover.
- Check if disposition set to OpalMCE_DISPOSITION_RECOVERED.
- Check if address at fault is inside kernel address space, if not then send
  SIGBUS to process if we hit exception when in userspace.
- If address at fault is not provided then and if we get a synchronous machine
  check while in userspace then kill the task.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 70 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
index 3276b409299c..a2b8c7b35fba 100644
--- a/arch/powerpc/include/asm/mce.h
+++ b/arch/powerpc/include/asm/mce.h
@@ -193,5 +193,6 @@ extern void release_mce_event(void);
 extern void machine_check_queue_event(void);
 extern void machine_check_process_queued_event(void);
 extern void machine_check_print_event_info(struct machine_check_event *evt);
+extern uint64_t get_mce_fault_addr(struct machine_check_event *evt);
 
 #endif /* __ASM_PPC64_MCE_H__ */
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index 1c6d15701c56..c0c52ec1fca7 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -316,3 +316,30 @@ void machine_check_print_event_info(struct machine_check_event *evt)
                 break;
         }
 }
+
+uint64_t get_mce_fault_addr(struct machine_check_event *evt)
+{
+        switch (evt->error_type) {
+        case MCE_ERROR_TYPE_UE:
+                if (evt->u.ue_error.effective_address_provided)
+                        return evt->u.ue_error.effective_address;
+                break;
+        case MCE_ERROR_TYPE_SLB:
+                if (evt->u.slb_error.effective_address_provided)
+                        return evt->u.slb_error.effective_address;
+                break;
+        case MCE_ERROR_TYPE_ERAT:
+                if (evt->u.erat_error.effective_address_provided)
+                        return evt->u.erat_error.effective_address;
+                break;
+        case MCE_ERROR_TYPE_TLB:
+                if (evt->u.tlb_error.effective_address_provided)
+                        return evt->u.tlb_error.effective_address;
+                break;
+        default:
+        case MCE_ERROR_TYPE_UNKNOWN:
+                break;
+        }
+        return 0;
+}
+EXPORT_SYMBOL(get_mce_fault_addr);
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index f348bd49487c..01e74cbc67e9 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -18,6 +18,7 @@
 #include <linux/interrupt.h>
 #include <linux/notifier.h>
 #include <linux/slab.h>
+#include <linux/sched.h>
 #include <linux/kobject.h>
 #include <asm/opal.h>
 #include <asm/firmware.h>
@@ -251,6 +252,44 @@ int opal_put_chars(uint32_t vtermno, const char *data, int total_len)
         return written;
 }
 
+static int opal_recover_mce(struct pt_regs *regs,
+                                        struct machine_check_event *evt)
+{
+        int recovered = 0;
+        uint64_t ea = get_mce_fault_addr(evt);
+
+        if (!(regs->msr & MSR_RI)) {
+                /* If MSR_RI isn't set, we cannot recover */
+                recovered = 0;
+        } else if (evt->disposition == MCE_DISPOSITION_RECOVERED) {
+                /* Platform corrected itself */
+                recovered = 1;
+        } else if (ea && !is_kernel_addr(ea)) {
+                /*
+                 * Faulting address is not in kernel text. We should be fine.
+                 * We need to find which process uses this address.
+                 * For now, kill the task if we have received exception when
+                 * in userspace.
+                 *
+                 * TODO: Queue up this address for hwpoisioning later.
+                 */
+                if (user_mode(regs) && !is_global_init(current)) {
+                        _exception(SIGBUS, regs, BUS_MCEERR_AR, regs->nip);
+                        recovered = 1;
+                } else
+                        recovered = 0;
+        } else if (user_mode(regs) && !is_global_init(current) &&
+                evt->severity == MCE_SEV_ERROR_SYNC) {
+                /*
+                 * If we have received a synchronous error when in userspace
+                 * kill the task.
+                 */
+                _exception(SIGBUS, regs, BUS_MCEERR_AR, regs->nip);
+                recovered = 1;
+        }
+        return recovered;
+}
+
 int opal_machine_check(struct pt_regs *regs)
 {
         struct machine_check_event evt;
@@ -266,7 +305,9 @@ int opal_machine_check(struct pt_regs *regs)
         }
         machine_check_print_event_info(&evt);
 
-        return evt.severity == MCE_SEV_FATAL ? 0 : 1;
+        if (opal_recover_mce(regs, &evt))
+                return 1;
+        return 0;
 }
 
 static irqreturn_t opal_interrupt(int irq, void *data)