4 files changed, 96 insertions, 70 deletions

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 51b26e895933..13eeea518233 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -183,11 +183,11 @@ typedef DECLARE_BITMAP(mce_banks_t, MAX_NR_BANKS);
 DECLARE_PER_CPU(mce_banks_t, mce_poll_banks);
 
 enum mcp_flags {
-        MCP_TIMESTAMP = (1 << 0),       /* log time stamp */
-        MCP_UC = (1 << 1),              /* log uncorrected errors */
-        MCP_DONTLOG = (1 << 2),         /* only clear, don't log */
+        MCP_TIMESTAMP   = BIT(0),       /* log time stamp */
+        MCP_UC          = BIT(1),       /* log uncorrected errors */
+        MCP_DONTLOG     = BIT(2),       /* only clear, don't log */
 };
-void machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
+bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
 
 int mce_notify_irq(void);
 void mce_notify_process(void);
diff --git a/arch/x86/kernel/cpu/mcheck/mce-internal.h b/arch/x86/kernel/cpu/mcheck/mce-internal.h
index 10b46906767f..e12f0bfb45c1 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-internal.h
+++ b/arch/x86/kernel/cpu/mcheck/mce-internal.h
@@ -14,6 +14,7 @@ enum severity_level {
 };
 
 #define ATTR_LEN                16
+#define INITIAL_CHECK_INTERVAL  5 * 60 /* 5 minutes */
 
 /* One object for each MCE bank, shared by all CPUs */
 struct mce_bank {
@@ -30,13 +31,13 @@ extern struct mce_bank *mce_banks;
 extern mce_banks_t mce_banks_ce_disabled;
 
 #ifdef CONFIG_X86_MCE_INTEL
-unsigned long mce_intel_adjust_timer(unsigned long interval);
-void mce_intel_cmci_poll(void);
+unsigned long cmci_intel_adjust_timer(unsigned long interval);
+bool mce_intel_cmci_poll(void);
 void mce_intel_hcpu_update(unsigned long cpu);
 void cmci_disable_bank(int bank);
 #else
-# define mce_intel_adjust_timer mce_adjust_timer_default
-static inline void mce_intel_cmci_poll(void) { }
+# define cmci_intel_adjust_timer mce_adjust_timer_default
+static inline bool mce_intel_cmci_poll(void) { return false; }
 static inline void mce_intel_hcpu_update(unsigned long cpu) { }
 static inline void cmci_disable_bank(int bank) { }
 #endif
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index d2c611699cd9..d60cbb8d78f7 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -58,7 +58,7 @@ static DEFINE_MUTEX(mce_chrdev_read_mutex);
 #define CREATE_TRACE_POINTS
 #include <trace/events/mce.h>
 
-#define SPINUNIT 100    /* 100ns */
+#define SPINUNIT                100     /* 100ns */
 
 DEFINE_PER_CPU(unsigned, mce_exception_count);
 
@@ -87,9 +87,6 @@ static DECLARE_WAIT_QUEUE_HEAD(mce_chrdev_wait);
 static DEFINE_PER_CPU(struct mce, mces_seen);
 static int                      cpu_missing;
 
-/* CMCI storm detection filter */
-static DEFINE_PER_CPU(unsigned long, mce_polled_error);
-
 /*
  * MCA banks polled by the period polling timer for corrected events.
  * With Intel CMCI, this only has MCA banks which do not support CMCI (if any).
@@ -623,8 +620,9 @@ DEFINE_PER_CPU(unsigned, mce_poll_count);
  * is already totally * confused. In this case it's likely it will
  * not fully execute the machine check handler either.
  */
-void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
+bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 {
+        bool error_logged = false;
         struct mce m;
         int severity;
         int i;
@@ -647,7 +645,7 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
                 if (!(m.status & MCI_STATUS_VAL))
                         continue;
 
-                this_cpu_write(mce_polled_error, 1);
+
                 /*
                  * Uncorrected or signalled events are handled by the exception
                  * handler when it is enabled, so don't process those here.
@@ -680,8 +678,10 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
                  * Don't get the IP here because it's unlikely to
                  * have anything to do with the actual error location.
                  */
-                if (!(flags & MCP_DONTLOG) && !mca_cfg.dont_log_ce)
+                if (!(flags & MCP_DONTLOG) && !mca_cfg.dont_log_ce) {
+                        error_logged = true;
                         mce_log(&m);
+                }
 
                 /*
                  * Clear state for this bank.
@@ -695,6 +695,8 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
          */
 
         sync_core();
+
+        return error_logged;
 }
 EXPORT_SYMBOL_GPL(machine_check_poll);
 
@@ -1311,7 +1313,7 @@ void mce_log_therm_throt_event(__u64 status)
  * poller finds an MCE, poll 2x faster.  When the poller finds no more
  * errors, poll 2x slower (up to check_interval seconds).
  */
-static unsigned long check_interval = 5 * 60; /* 5 minutes */
+static unsigned long check_interval = INITIAL_CHECK_INTERVAL;
 
 static DEFINE_PER_CPU(unsigned long, mce_next_interval); /* in jiffies */
 static DEFINE_PER_CPU(struct timer_list, mce_timer);
@@ -1321,49 +1323,57 @@ static unsigned long mce_adjust_timer_default(unsigned long interval)
         return interval;
 }
 
-static unsigned long (*mce_adjust_timer)(unsigned long interval) =
-        mce_adjust_timer_default;
+static unsigned long (*mce_adjust_timer)(unsigned long interval) = mce_adjust_timer_default;
 
-static int cmc_error_seen(void)
+static void __restart_timer(struct timer_list *t, unsigned long interval)
 {
-        unsigned long *v = this_cpu_ptr(&mce_polled_error);
+        unsigned long when = jiffies + interval;
+        unsigned long flags;
 
-        return test_and_clear_bit(0, v);
+        local_irq_save(flags);
+
+        if (timer_pending(t)) {
+                if (time_before(when, t->expires))
+                        mod_timer_pinned(t, when);
+        } else {
+                t->expires = round_jiffies(when);
+                add_timer_on(t, smp_processor_id());
+        }
+
+        local_irq_restore(flags);
 }
 
 static void mce_timer_fn(unsigned long data)
 {
         struct timer_list *t = this_cpu_ptr(&mce_timer);
+        int cpu = smp_processor_id();
         unsigned long iv;
-        int notify;
 
-        WARN_ON(smp_processor_id() != data);
+        WARN_ON(cpu != data);
+
+        iv = __this_cpu_read(mce_next_interval);
 
         if (mce_available(this_cpu_ptr(&cpu_info))) {
-                machine_check_poll(MCP_TIMESTAMP,
-                                this_cpu_ptr(&mce_poll_banks));
-                mce_intel_cmci_poll();
+                machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_poll_banks));
+
+                if (mce_intel_cmci_poll()) {
+                        iv = mce_adjust_timer(iv);
+                        goto done;
+                }
         }
 
         /*
-         * Alert userspace if needed.  If we logged an MCE, reduce the
-         * polling interval, otherwise increase the polling interval.
+         * Alert userspace if needed. If we logged an MCE, reduce the polling
+         * interval, otherwise increase the polling interval.
          */
-        iv = __this_cpu_read(mce_next_interval);
-        notify = mce_notify_irq();
-        notify |= cmc_error_seen();
-        if (notify) {
+        if (mce_notify_irq())
                 iv = max(iv / 2, (unsigned long) HZ/100);
-        } else {
+        else
                 iv = min(iv * 2, round_jiffies_relative(check_interval * HZ));
-                iv = mce_adjust_timer(iv);
-        }
+
+done:
         __this_cpu_write(mce_next_interval, iv);
-        /* Might have become 0 after CMCI storm subsided */
-        if (iv) {
-                t->expires = jiffies + iv;
-                add_timer_on(t, smp_processor_id());
-        }
+        __restart_timer(t, iv);
 }
 
 /*
@@ -1372,16 +1382,10 @@ static void mce_timer_fn(unsigned long data)
 void mce_timer_kick(unsigned long interval)
 {
         struct timer_list *t = this_cpu_ptr(&mce_timer);
-        unsigned long when = jiffies + interval;
         unsigned long iv = __this_cpu_read(mce_next_interval);
 
-        if (timer_pending(t)) {
-                if (time_before(when, t->expires))
-                        mod_timer_pinned(t, when);
-        } else {
-                t->expires = round_jiffies(when);
-                add_timer_on(t, smp_processor_id());
-        }
+        __restart_timer(t, interval);
+
         if (interval < iv)
                 __this_cpu_write(mce_next_interval, interval);
 }
@@ -1682,7 +1686,7 @@ static void __mcheck_cpu_init_vendor(struct cpuinfo_x86 *c)
         switch (c->x86_vendor) {
         case X86_VENDOR_INTEL:
                 mce_intel_feature_init(c);
-                mce_adjust_timer = mce_intel_adjust_timer;
+                mce_adjust_timer = cmci_intel_adjust_timer;
                 break;
         case X86_VENDOR_AMD:
                 mce_amd_feature_init(c);
diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index b3c97bafc123..b4a41cf030ed 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -39,6 +39,15 @@
 static DEFINE_PER_CPU(mce_banks_t, mce_banks_owned);
 
 /*
+ * CMCI storm detection backoff counter
+ *
+ * During storm, we reset this counter to INITIAL_CHECK_INTERVAL in case we've
+ * encountered an error. If not, we decrement it by one. We signal the end of
+ * the CMCI storm when it reaches 0.
+ */
+static DEFINE_PER_CPU(int, cmci_backoff_cnt);
+
+/*
  * cmci_discover_lock protects against parallel discovery attempts
  * which could race against each other.
  */
@@ -46,7 +55,7 @@ static DEFINE_RAW_SPINLOCK(cmci_discover_lock);
 
 #define CMCI_THRESHOLD          1
 #define CMCI_POLL_INTERVAL      (30 * HZ)
-#define CMCI_STORM_INTERVAL     (1 * HZ)
+#define CMCI_STORM_INTERVAL     (HZ)
 #define CMCI_STORM_THRESHOLD    15
 
 static DEFINE_PER_CPU(unsigned long, cmci_time_stamp);
@@ -82,11 +91,21 @@ static int cmci_supported(int *banks)
         return !!(cap & MCG_CMCI_P);
 }
 
-void mce_intel_cmci_poll(void)
+bool mce_intel_cmci_poll(void)
 {
         if (__this_cpu_read(cmci_storm_state) == CMCI_STORM_NONE)
-                return;
-        machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
+                return false;
+
+        /*
+         * Reset the counter if we've logged an error in the last poll
+         * during the storm.
+         */
+        if (machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned)))
+                this_cpu_write(cmci_backoff_cnt, INITIAL_CHECK_INTERVAL);
+        else
+                this_cpu_dec(cmci_backoff_cnt);
+
+        return true;
 }
 
 void mce_intel_hcpu_update(unsigned long cpu)
@@ -97,31 +116,32 @@ void mce_intel_hcpu_update(unsigned long cpu)
         per_cpu(cmci_storm_state, cpu) = CMCI_STORM_NONE;
 }
 
-unsigned long mce_intel_adjust_timer(unsigned long interval)
+unsigned long cmci_intel_adjust_timer(unsigned long interval)
 {
-        int r;
-
-        if (interval < CMCI_POLL_INTERVAL)
-                return interval;
+        if ((this_cpu_read(cmci_backoff_cnt) > 0) &&
+            (__this_cpu_read(cmci_storm_state) == CMCI_STORM_ACTIVE)) {
+                mce_notify_irq();
+                return CMCI_STORM_INTERVAL;
+        }
 
         switch (__this_cpu_read(cmci_storm_state)) {
         case CMCI_STORM_ACTIVE:
+
                 /*
                  * We switch back to interrupt mode once the poll timer has
-                 * silenced itself. That means no events recorded and the
-                 * timer interval is back to our poll interval.
+                 * silenced itself. That means no events recorded and the timer
+                 * interval is back to our poll interval.
                  */
                 __this_cpu_write(cmci_storm_state, CMCI_STORM_SUBSIDED);
-                r = atomic_sub_return(1, &cmci_storm_on_cpus);
-                if (r == 0)
+                if (!atomic_sub_return(1, &cmci_storm_on_cpus))
                         pr_notice("CMCI storm subsided: switching to interrupt mode\n");
+
                 /* FALLTHROUGH */
 
         case CMCI_STORM_SUBSIDED:
                 /*
-                 * We wait for all cpus to go back to SUBSIDED
-                 * state. When that happens we switch back to
-                 * interrupt mode.
+                 * We wait for all CPUs to go back to SUBSIDED state. When that
+                 * happens we switch back to interrupt mode.
                  */
                 if (!atomic_read(&cmci_storm_on_cpus)) {
                         __this_cpu_write(cmci_storm_state, CMCI_STORM_NONE);
@@ -130,10 +150,8 @@ unsigned long mce_intel_adjust_timer(unsigned long interval)
                 }
                 return CMCI_POLL_INTERVAL;
         default:
-                /*
-                 * We have shiny weather. Let the poll do whatever it
-                 * thinks.
-                 */
+
+                /* We have shiny weather. Let the poll do whatever it thinks. */
                 return interval;
         }
 }
@@ -178,7 +196,8 @@ static bool cmci_storm_detect(void)
         cmci_storm_disable_banks();
         __this_cpu_write(cmci_storm_state, CMCI_STORM_ACTIVE);
         r = atomic_add_return(1, &cmci_storm_on_cpus);
-        mce_timer_kick(CMCI_POLL_INTERVAL);
+        mce_timer_kick(CMCI_STORM_INTERVAL);
+        this_cpu_write(cmci_backoff_cnt, INITIAL_CHECK_INTERVAL);
 
         if (r == 1)
                 pr_notice("CMCI storm detected: switching to poll mode\n");
@@ -195,6 +214,7 @@ static void intel_threshold_interrupt(void)
 {
         if (cmci_storm_detect())
                 return;
+
         machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
         mce_notify_irq();
 }
@@ -286,6 +306,7 @@ void cmci_recheck(void)
 
         if (!mce_available(raw_cpu_ptr(&cpu_info)) || !cmci_supported(&banks))
                 return;
+
         local_irq_save(flags);
         machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
         local_irq_restore(flags);