powerpc/book3s: Queue up and process delayed MCE events.

When machine check real mode handler can not continue into host kernel
in V mode, it returns from the interrupt and we loose MCE event which
never gets logged. In such a situation queue up the MCE event so that
we can log it later when we get back into host kernel with r1 pointing to
kernel stack e.g. during syscall exit.

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

5 files changed, 168 insertions, 98 deletions

diff --git a/arch/powerpc/include/asm/mce.h b/arch/powerpc/include/asm/mce.h
index 87cad2a808c2..3276b409299c 100644
--- a/arch/powerpc/include/asm/mce.h
+++ b/arch/powerpc/include/asm/mce.h
@@ -190,5 +190,8 @@ extern void save_mce_event(struct pt_regs *regs, long handled,
                            struct mce_error_info *mce_err, uint64_t addr);
 extern int get_mce_event(struct machine_check_event *mce, bool release);
 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);
 
 #endif /* __ASM_PPC64_MCE_H__ */
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index bbfb0294b354..770d6d65c47b 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -184,6 +184,11 @@ syscall_exit:
         bl      .do_show_syscall_exit
         ld      r3,RESULT(r1)
 #endif
+#ifdef CONFIG_PPC_BOOK3S_64
+BEGIN_FTR_SECTION
+        bl      .machine_check_process_queued_event
+END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
+#endif
         CURRENT_THREAD_INFO(r12, r1)
 
         ld      r8,_MSR(r1)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 1aec3025eeee..862b9dd4a9db 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -855,7 +855,8 @@ BEGIN_FTR_SECTION
         /* Supervisor state loss */
         li      r0,1
         stb     r0,PACA_NAPSTATELOST(r13)
-3:      MACHINE_CHECK_HANDLER_WINDUP
+3:      bl      .machine_check_queue_event
+        MACHINE_CHECK_HANDLER_WINDUP
         GET_PACA(r13)
         ld      r1,PACAR1(r13)
         b       .power7_enter_nap_mode
@@ -895,8 +896,10 @@ BEGIN_FTR_SECTION
 2:
         /*
          * Return from MC interrupt.
-         * TODO: Queue up the MCE event so that we can log it later.
+         * Queue up the MCE event so that we can log it later, while
+         * returning from kernel or opal call.
          */
+        bl      .machine_check_queue_event
         MACHINE_CHECK_HANDLER_WINDUP
         rfid
 9:
diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index aeecdf1ba897..1c6d15701c56 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -31,6 +31,10 @@
 static DEFINE_PER_CPU(int, mce_nest_count);
 static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event);
 
+/* Queue for delayed MCE events. */
+static DEFINE_PER_CPU(int, mce_queue_count);
+static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event_queue);
+
 static void mce_set_error_info(struct machine_check_event *mce,
                                struct mce_error_info *mce_err)
 {
@@ -162,3 +166,153 @@ void release_mce_event(void)
 {
         get_mce_event(NULL, true);
 }
+
+/*
+ * Queue up the MCE event which then can be handled later.
+ */
+void machine_check_queue_event(void)
+{
+        int index;
+        struct machine_check_event evt;
+
+        if (!get_mce_event(&evt, MCE_EVENT_RELEASE))
+                return;
+
+        index = __get_cpu_var(mce_queue_count)++;
+        /* If queue is full, just return for now. */
+        if (index >= MAX_MC_EVT) {
+                __get_cpu_var(mce_queue_count)--;
+                return;
+        }
+        __get_cpu_var(mce_event_queue[index]) = evt;
+}
+
+/*
+ * process pending MCE event from the mce event queue. This function will be
+ * called during syscall exit.
+ */
+void machine_check_process_queued_event(void)
+{
+        int index;
+
+        preempt_disable();
+        /*
+         * For now just print it to console.
+         * TODO: log this error event to FSP or nvram.
+         */
+        while (__get_cpu_var(mce_queue_count) > 0) {
+                index = __get_cpu_var(mce_queue_count) - 1;
+                machine_check_print_event_info(
+                                &__get_cpu_var(mce_event_queue[index]));
+                __get_cpu_var(mce_queue_count)--;
+        }
+        preempt_enable();
+}
+
+void machine_check_print_event_info(struct machine_check_event *evt)
+{
+        const char *level, *sevstr, *subtype;
+        static const char *mc_ue_types[] = {
+                "Indeterminate",
+                "Instruction fetch",
+                "Page table walk ifetch",
+                "Load/Store",
+                "Page table walk Load/Store",
+        };
+        static const char *mc_slb_types[] = {
+                "Indeterminate",
+                "Parity",
+                "Multihit",
+        };
+        static const char *mc_erat_types[] = {
+                "Indeterminate",
+                "Parity",
+                "Multihit",
+        };
+        static const char *mc_tlb_types[] = {
+                "Indeterminate",
+                "Parity",
+                "Multihit",
+        };
+
+        /* Print things out */
+        if (evt->version != MCE_V1) {
+                pr_err("Machine Check Exception, Unknown event version %d !\n",
+                       evt->version);
+                return;
+        }
+        switch (evt->severity) {
+        case MCE_SEV_NO_ERROR:
+                level = KERN_INFO;
+                sevstr = "Harmless";
+                break;
+        case MCE_SEV_WARNING:
+                level = KERN_WARNING;
+                sevstr = "";
+                break;
+        case MCE_SEV_ERROR_SYNC:
+                level = KERN_ERR;
+                sevstr = "Severe";
+                break;
+        case MCE_SEV_FATAL:
+        default:
+                level = KERN_ERR;
+                sevstr = "Fatal";
+                break;
+        }
+
+        printk("%s%s Machine check interrupt [%s]\n", level, sevstr,
+               evt->disposition == MCE_DISPOSITION_RECOVERED ?
+               "Recovered" : "[Not recovered");
+        printk("%s  Initiator: %s\n", level,
+               evt->initiator == MCE_INITIATOR_CPU ? "CPU" : "Unknown");
+        switch (evt->error_type) {
+        case MCE_ERROR_TYPE_UE:
+                subtype = evt->u.ue_error.ue_error_type <
+                        ARRAY_SIZE(mc_ue_types) ?
+                        mc_ue_types[evt->u.ue_error.ue_error_type]
+                        : "Unknown";
+                printk("%s  Error type: UE [%s]\n", level, subtype);
+                if (evt->u.ue_error.effective_address_provided)
+                        printk("%s    Effective address: %016llx\n",
+                               level, evt->u.ue_error.effective_address);
+                if (evt->u.ue_error.physical_address_provided)
+                        printk("%s      Physial address: %016llx\n",
+                               level, evt->u.ue_error.physical_address);
+                break;
+        case MCE_ERROR_TYPE_SLB:
+                subtype = evt->u.slb_error.slb_error_type <
+                        ARRAY_SIZE(mc_slb_types) ?
+                        mc_slb_types[evt->u.slb_error.slb_error_type]
+                        : "Unknown";
+                printk("%s  Error type: SLB [%s]\n", level, subtype);
+                if (evt->u.slb_error.effective_address_provided)
+                        printk("%s    Effective address: %016llx\n",
+                               level, evt->u.slb_error.effective_address);
+                break;
+        case MCE_ERROR_TYPE_ERAT:
+                subtype = evt->u.erat_error.erat_error_type <
+                        ARRAY_SIZE(mc_erat_types) ?
+                        mc_erat_types[evt->u.erat_error.erat_error_type]
+                        : "Unknown";
+                printk("%s  Error type: ERAT [%s]\n", level, subtype);
+                if (evt->u.erat_error.effective_address_provided)
+                        printk("%s    Effective address: %016llx\n",
+                               level, evt->u.erat_error.effective_address);
+                break;
+        case MCE_ERROR_TYPE_TLB:
+                subtype = evt->u.tlb_error.tlb_error_type <
+                        ARRAY_SIZE(mc_tlb_types) ?
+                        mc_tlb_types[evt->u.tlb_error.tlb_error_type]
+                        : "Unknown";
+                printk("%s  Error type: TLB [%s]\n", level, subtype);
+                if (evt->u.tlb_error.effective_address_provided)
+                        printk("%s    Effective address: %016llx\n",
+                               level, evt->u.tlb_error.effective_address);
+                break;
+        default:
+        case MCE_ERROR_TYPE_UNKNOWN:
+                printk("%s  Error type: Unknown\n", level);
+                break;
+        }
+}
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index c5e71d773f47..245096f90437 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -258,29 +258,6 @@ int opal_put_chars(uint32_t vtermno, const char *data, int total_len)
 int opal_machine_check(struct pt_regs *regs)
 {
         struct machine_check_event evt;
-        const char *level, *sevstr, *subtype;
-        static const char *opal_mc_ue_types[] = {
-                "Indeterminate",
-                "Instruction fetch",
-                "Page table walk ifetch",
-                "Load/Store",
-                "Page table walk Load/Store",
-        };
-        static const char *opal_mc_slb_types[] = {
-                "Indeterminate",
-                "Parity",
-                "Multihit",
-        };
-        static const char *opal_mc_erat_types[] = {
-                "Indeterminate",
-                "Parity",
-                "Multihit",
-        };
-        static const char *opal_mc_tlb_types[] = {
-                "Indeterminate",
-                "Parity",
-                "Multihit",
-        };
 
         if (!get_mce_event(&evt, MCE_EVENT_RELEASE))
                 return 0;
@@ -291,80 +268,8 @@ int opal_machine_check(struct pt_regs *regs)
                        evt.version);
                 return 0;
         }
-        switch(evt.severity) {
-        case MCE_SEV_NO_ERROR:
-                level = KERN_INFO;
-                sevstr = "Harmless";
-                break;
-        case MCE_SEV_WARNING:
-                level = KERN_WARNING;
-                sevstr = "";
-                break;
-        case MCE_SEV_ERROR_SYNC:
-                level = KERN_ERR;
-                sevstr = "Severe";
-                break;
-        case MCE_SEV_FATAL:
-        default:
-                level = KERN_ERR;
-                sevstr = "Fatal";
-                break;
-        }
+        machine_check_print_event_info(&evt);
 
-        printk("%s%s Machine check interrupt [%s]\n", level, sevstr,
-               evt.disposition == MCE_DISPOSITION_RECOVERED ?
-               "Recovered" : "[Not recovered");
-        printk("%s  Initiator: %s\n", level,
-               evt.initiator == MCE_INITIATOR_CPU ? "CPU" : "Unknown");
-        switch(evt.error_type) {
-        case MCE_ERROR_TYPE_UE:
-                subtype = evt.u.ue_error.ue_error_type <
-                        ARRAY_SIZE(opal_mc_ue_types) ?
-                        opal_mc_ue_types[evt.u.ue_error.ue_error_type]
-                        : "Unknown";
-                printk("%s  Error type: UE [%s]\n", level, subtype);
-                if (evt.u.ue_error.effective_address_provided)
-                        printk("%s    Effective address: %016llx\n",
-                               level, evt.u.ue_error.effective_address);
-                if (evt.u.ue_error.physical_address_provided)
-                        printk("%s      Physial address: %016llx\n",
-                               level, evt.u.ue_error.physical_address);
-                break;
-        case MCE_ERROR_TYPE_SLB:
-                subtype = evt.u.slb_error.slb_error_type <
-                        ARRAY_SIZE(opal_mc_slb_types) ?
-                        opal_mc_slb_types[evt.u.slb_error.slb_error_type]
-                        : "Unknown";
-                printk("%s  Error type: SLB [%s]\n", level, subtype);
-                if (evt.u.slb_error.effective_address_provided)
-                        printk("%s    Effective address: %016llx\n",
-                               level, evt.u.slb_error.effective_address);
-                break;
-        case MCE_ERROR_TYPE_ERAT:
-                subtype = evt.u.erat_error.erat_error_type <
-                        ARRAY_SIZE(opal_mc_erat_types) ?
-                        opal_mc_erat_types[evt.u.erat_error.erat_error_type]
-                        : "Unknown";
-                printk("%s  Error type: ERAT [%s]\n", level, subtype);
-                if (evt.u.erat_error.effective_address_provided)
-                        printk("%s    Effective address: %016llx\n",
-                               level, evt.u.erat_error.effective_address);
-                break;
-        case MCE_ERROR_TYPE_TLB:
-                subtype = evt.u.tlb_error.tlb_error_type <
-                        ARRAY_SIZE(opal_mc_tlb_types) ?
-                        opal_mc_tlb_types[evt.u.tlb_error.tlb_error_type]
-                        : "Unknown";
-                printk("%s  Error type: TLB [%s]\n", level, subtype);
-                if (evt.u.tlb_error.effective_address_provided)
-                        printk("%s    Effective address: %016llx\n",
-                               level, evt.u.tlb_error.effective_address);
-                break;
-        default:
-        case MCE_ERROR_TYPE_UNKNOWN:
-                printk("%s  Error type: Unknown\n", level);
-                break;
-        }
         return evt.severity == MCE_SEV_FATAL ? 0 : 1;
 }