Merge branch 'x86-ras-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 RAS changes from Ingo Molnar:
 "The main changes in this cycle were:

   - Simplify the CMCI storm logic on Intel CPUs after yet another
     report about a race in the code (Borislav Petkov)

   - Enable the MCE threshold irq on AMD CPUs by default (Aravind
     Gopalakrishnan)

   - Add AMD-specific MCE-severity grading function.  Further error
     recovery actions will be based on its output (Aravind Gopalakrishnan)

   - Documentation updates (Borislav Petkov)

   - ... assorted fixes and cleanups"

* 'x86-ras-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mce/severity: Fix warning about indented braces
  x86/mce: Define mce_severity function pointer
  x86/mce: Add an AMD severities-grading function
  x86/mce: Reindent __mcheck_cpu_apply_quirks() properly
  x86/mce: Use safe MSR accesses for AMD quirk
  x86/MCE/AMD: Enable thresholding interrupts by default if supported
  x86/MCE: Make mce_panic() fatal machine check msg in the same pattern
  x86/MCE/intel: Cleanup CMCI storm logic
  Documentation/acpi/einj: Correct and streamline text
  x86/MCE/AMD: Drop bogus const modifier from AMD's bank4_names()

6 files changed, 214 insertions, 107 deletions

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 9b3de99dc004..1f5a86d518db 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -116,6 +116,12 @@ struct mca_config {
 	u32 rip_msr;
 };
 
+struct mce_vendor_flags {
+	__u64		overflow_recov	: 1, /* cpuid_ebx(80000007) */
+			__reserved_0	: 63;
+};
+extern struct mce_vendor_flags mce_flags;
+
 extern struct mca_config mca_cfg;
 extern void mce_register_decode_chain(struct notifier_block *nb);
 extern void mce_unregister_decode_chain(struct notifier_block *nb);
@@ -128,9 +134,11 @@ extern int mce_p5_enabled;
 #ifdef CONFIG_X86_MCE
 int mcheck_init(void);
 void mcheck_cpu_init(struct cpuinfo_x86 *c);
+void mcheck_vendor_init_severity(void);
 #else
 static inline int mcheck_init(void) { return 0; }
 static inline void mcheck_cpu_init(struct cpuinfo_x86 *c) {}
+static inline void mcheck_vendor_init_severity(void) {}
 #endif
 
 #ifdef CONFIG_X86_ANCIENT_MCE
@@ -183,11 +191,11 @@ 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);
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce-internal.h b/arch/x86/kernel/cpu/mcheck/mce-internal.h
index 10b46906767f..fe32074b865b 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 {
@@ -23,20 +24,20 @@ struct mce_bank {
 	char			attrname[ATTR_LEN];	/* attribute name */
 };
 
-int mce_severity(struct mce *a, int tolerant, char **msg, bool is_excp);
+extern int (*mce_severity)(struct mce *a, int tolerant, char **msg, bool is_excp);
 struct dentry *mce_get_debugfs_dir(void);
 
 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-severity.c b/arch/x86/kernel/cpu/mcheck/mce-severity.c
index 8bb433043a7f..9c682c222071 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-severity.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c
@@ -186,7 +186,61 @@ static int error_context(struct mce *m)
 	return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL;
 }
 
-int mce_severity(struct mce *m, int tolerant, char **msg, bool is_excp)
+/*
+ * See AMD Error Scope Hierarchy table in a newer BKDG. For example
+ * 49125_15h_Models_30h-3Fh_BKDG.pdf, section "RAS Features"
+ */
+static int mce_severity_amd(struct mce *m, int tolerant, char **msg, bool is_excp)
+{
+	enum context ctx = error_context(m);
+
+	/* Processor Context Corrupt, no need to fumble too much, die! */
+	if (m->status & MCI_STATUS_PCC)
+		return MCE_PANIC_SEVERITY;
+
+	if (m->status & MCI_STATUS_UC) {
+
+		/*
+		 * On older systems where overflow_recov flag is not present, we
+		 * should simply panic if an error overflow occurs. If
+		 * overflow_recov flag is present and set, then software can try
+		 * to at least kill process to prolong system operation.
+		 */
+		if (mce_flags.overflow_recov) {
+			/* software can try to contain */
+			if (!(m->mcgstatus & MCG_STATUS_RIPV) && (ctx == IN_KERNEL))
+				return MCE_PANIC_SEVERITY;
+
+			/* kill current process */
+			return MCE_AR_SEVERITY;
+		} else {
+			/* at least one error was not logged */
+			if (m->status & MCI_STATUS_OVER)
+				return MCE_PANIC_SEVERITY;
+		}
+
+		/*
+		 * For any other case, return MCE_UC_SEVERITY so that we log the
+		 * error and exit #MC handler.
+		 */
+		return MCE_UC_SEVERITY;
+	}
+
+	/*
+	 * deferred error: poll handler catches these and adds to mce_ring so
+	 * memory-failure can take recovery actions.
+	 */
+	if (m->status & MCI_STATUS_DEFERRED)
+		return MCE_DEFERRED_SEVERITY;
+
+	/*
+	 * corrected error: poll handler catches these and passes responsibility
+	 * of decoding the error to EDAC
+	 */
+	return MCE_KEEP_SEVERITY;
+}
+
+static int mce_severity_intel(struct mce *m, int tolerant, char **msg, bool is_excp)
 {
 	enum exception excp = (is_excp ? EXCP_CONTEXT : NO_EXCP);
 	enum context ctx = error_context(m);
@@ -216,6 +270,16 @@ int mce_severity(struct mce *m, int tolerant, char **msg, bool is_excp)
 	}
 }
 
+/* Default to mce_severity_intel */
+int (*mce_severity)(struct mce *m, int tolerant, char **msg, bool is_excp) =
+		    mce_severity_intel;
+
+void __init mcheck_vendor_init_severity(void)
+{
+	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
+		mce_severity = mce_severity_amd;
+}
+
 #ifdef CONFIG_DEBUG_FS
 static void *s_start(struct seq_file *f, loff_t *pos)
 {
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 3c036cb4a370..e535533d5ab8 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -60,11 +60,12 @@ 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);
 
 struct mce_bank *mce_banks __read_mostly;
+struct mce_vendor_flags mce_flags __read_mostly;
 
 struct mca_config mca_cfg __read_mostly = {
 	.bootlog  = -1,
@@ -89,9 +90,6 @@ 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).
@@ -622,8 +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;
@@ -646,7 +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.
@@ -679,8 +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.
@@ -694,6 +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);
 
@@ -813,7 +816,7 @@ static void mce_reign(void)
 	 * other CPUs.
 	 */
 	if (m && global_worst >= MCE_PANIC_SEVERITY && mca_cfg.tolerant < 3)
-		mce_panic("Fatal Machine check", m, msg);
+		mce_panic("Fatal machine check", m, msg);
 
 	/*
 	 * For UC somewhere we let the CPU who detects it handle it.
@@ -826,7 +829,7 @@ static void mce_reign(void)
 	 * source or one CPU is hung. Panic.
 	 */
 	if (global_worst <= MCE_KEEP_SEVERITY && mca_cfg.tolerant < 3)
-		mce_panic("Machine check from unknown source", NULL, NULL);
+		mce_panic("Fatal machine check from unknown source", NULL, NULL);
 
 	/*
 	 * Now clear all the mces_seen so that they don't reappear on
@@ -1258,7 +1261,7 @@ 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);
@@ -1268,49 +1271,57 @@ 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;
+
+	local_irq_save(flags);
 
-	return test_and_clear_bit(0, v);
+	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);
 }
 
 /*
@@ -1319,16 +1330,10 @@ 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);
 }
@@ -1525,45 +1530,46 @@ static int __mcheck_cpu_apply_quirks(struct cpuinfo_x86 *c)
 		 * Various K7s with broken bank 0 around. Always disable
 		 * by default.
 		 */
-		 if (c->x86 == 6 && cfg->banks > 0)
+		if (c->x86 == 6 && cfg->banks > 0)
 			mce_banks[0].ctl = 0;
 
-		 /*
-		  * Turn off MC4_MISC thresholding banks on those models since
-		  * they're not supported there.
-		  */
-		 if (c->x86 == 0x15 &&
-		     (c->x86_model >= 0x10 && c->x86_model <= 0x1f)) {
-			 int i;
-			 u64 val, hwcr;
-			 bool need_toggle;
-			 u32 msrs[] = {
+		/*
+		 * overflow_recov is supported for F15h Models 00h-0fh
+		 * even though we don't have a CPUID bit for it.
+		 */
+		if (c->x86 == 0x15 && c->x86_model <= 0xf)
+			mce_flags.overflow_recov = 1;
+
+		/*
+		 * Turn off MC4_MISC thresholding banks on those models since
+		 * they're not supported there.
+		 */
+		if (c->x86 == 0x15 &&
+		    (c->x86_model >= 0x10 && c->x86_model <= 0x1f)) {
+			int i;
+			u64 hwcr;
+			bool need_toggle;
+			u32 msrs[] = {
 				0x00000413, /* MC4_MISC0 */
 				0xc0000408, /* MC4_MISC1 */
-			 };
+			};
 
-			 rdmsrl(MSR_K7_HWCR, hwcr);
+			rdmsrl(MSR_K7_HWCR, hwcr);
 
-			 /* McStatusWrEn has to be set */
-			 need_toggle = !(hwcr & BIT(18));
+			/* McStatusWrEn has to be set */
+			need_toggle = !(hwcr & BIT(18));
 
-			 if (need_toggle)
-				 wrmsrl(MSR_K7_HWCR, hwcr | BIT(18));
+			if (need_toggle)
+				wrmsrl(MSR_K7_HWCR, hwcr | BIT(18));
 
-			 for (i = 0; i < ARRAY_SIZE(msrs); i++) {
-				 rdmsrl(msrs[i], val);
+			/* Clear CntP bit safely */
+			for (i = 0; i < ARRAY_SIZE(msrs); i++)
+				msr_clear_bit(msrs[i], 62);
 
-				 /* CntP bit set? */
-				 if (val & BIT_64(62)) {
-					val &= ~BIT_64(62);
-					wrmsrl(msrs[i], val);
-				 }
-			 }
-
-			 /* restore old settings */
-			 if (need_toggle)
-				 wrmsrl(MSR_K7_HWCR, hwcr);
-		 }
+			/* restore old settings */
+			if (need_toggle)
+				wrmsrl(MSR_K7_HWCR, hwcr);
+		}
 	}
 
 	if (c->x86_vendor == X86_VENDOR_INTEL) {
@@ -1629,10 +1635,11 @@ 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);
+		mce_flags.overflow_recov = cpuid_ebx(0x80000007) & 0x1;
 		break;
 	default:
 		break;
@@ -2017,6 +2024,7 @@ __setup("mce", mcheck_enable);
 int __init mcheck_init(void)
 {
 	mcheck_intel_therm_init();
+	mcheck_vendor_init_severity();
 
 	return 0;
 }
diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index f1c3769bbd64..55ad9b37cae8 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -79,7 +79,7 @@ static inline bool is_shared_bank(int bank)
 	return (bank == 4);
 }
 
-static const char * const bank4_names(struct threshold_block *b)
+static const char *bank4_names(const struct threshold_block *b)
 {
 	switch (b->address) {
 	/* MSR4_MISC0 */
@@ -250,6 +250,7 @@ void mce_amd_feature_init(struct cpuinfo_x86 *c)
 			if (!b.interrupt_capable)
 				goto init;
 
+			b.interrupt_enable = 1;
 			new	= (high & MASK_LVTOFF_HI) >> 20;
 			offset  = setup_APIC_mce(offset, new);
 
@@ -322,6 +323,8 @@ static void amd_threshold_interrupt(void)
 log:
 	mce_setup(&m);
 	rdmsrl(MSR_IA32_MCx_STATUS(bank), m.status);
+	if (!(m.status & MCI_STATUS_VAL))
+		return;
 	m.misc = ((u64)high << 32) | low;
 	m.bank = bank;
 	mce_log(&m);
@@ -497,10 +500,12 @@ static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank,
 	b->interrupt_capable	= lvt_interrupt_supported(bank, high);
 	b->threshold_limit	= THRESHOLD_MAX;
 
-	if (b->interrupt_capable)
+	if (b->interrupt_capable) {
 		threshold_ktype.default_attrs[2] = &interrupt_enable.attr;
-	else
+		b->interrupt_enable = 1;
+	} else {
 		threshold_ktype.default_attrs[2] = NULL;
+	}
 
 	INIT_LIST_HEAD(&b->miscj);
 
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);