Merge tag 'ras_for_3.21' of git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras into x86/ras

Pull RAS updates from Borislav Petkov:

 "- Enable AMD thresholding IRQ by default if supported. (Aravind Gopalakrishnan)

  - Unify mce_panic() message pattern. (Derek Che)

  - A bit more involved simplification of the CMCI logic after yet another
    report about race condition with the adaptive logic. (Borislav Petkov)

  - ACPI APEI EINJ fleshing out of the user documentation. (Borislav Petkov)

  - Minor cleanup. (Jan Beulich.)"

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/acpi/apei/einj.txt

@@ -1,129 +1,177 @@
 			APEI Error INJection
 			~~~~~~~~~~~~~~~~~~~~
 
-EINJ provides a hardware error injection mechanism
-It is very useful for debugging and testing of other APEI and RAS features.
+EINJ provides a hardware error injection mechanism. It is very useful
+for debugging and testing APEI and RAS features in general.
 
-To use EINJ, make sure the following are enabled in your kernel
+You need to check whether your BIOS supports EINJ first. For that, look
+for early boot messages similar to this one:
+
+ACPI: EINJ 0x000000007370A000 000150 (v01 INTEL           00000001 INTL 00000001)
+
+which shows that the BIOS is exposing an EINJ table - it is the
+mechanism through which the injection is done.
+
+Alternatively, look in /sys/firmware/acpi/tables for an "EINJ" file,
+which is a different representation of the same thing.
+
+It doesn't necessarily mean that EINJ is not supported if those above
+don't exist: before you give up, go into BIOS setup to see if the BIOS
+has an option to enable error injection. Look for something called WHEA
+or similar. Often, you need to enable an ACPI5 support option prior, in
+order to see the APEI,EINJ,... functionality supported and exposed by
+the BIOS menu.
+
+To use EINJ, make sure the following are options enabled in your kernel
 configuration:
 
 CONFIG_DEBUG_FS
 CONFIG_ACPI_APEI
 CONFIG_ACPI_APEI_EINJ
 
-The user interface of EINJ is debug file system, under the
-directory apei/einj. The following files are provided.
+The EINJ user interface is in <debugfs mount point>/apei/einj.
+
+The following files belong to it:
 
 - available_error_type
-  Reading this file returns the error injection capability of the
-  platform, that is, which error types are supported. The error type
-  definition is as follow, the left field is the error type value, the
-  right field is error description.
-
-    0x00000001	Processor Correctable
-    0x00000002	Processor Uncorrectable non-fatal
-    0x00000004	Processor Uncorrectable fatal
-    0x00000008  Memory Correctable
-    0x00000010  Memory Uncorrectable non-fatal
-    0x00000020  Memory Uncorrectable fatal
-    0x00000040	PCI Express Correctable
-    0x00000080	PCI Express Uncorrectable fatal
-    0x00000100	PCI Express Uncorrectable non-fatal
-    0x00000200	Platform Correctable
-    0x00000400	Platform Uncorrectable non-fatal
-    0x00000800	Platform Uncorrectable fatal
-
-  The format of file contents are as above, except there are only the
-  available error type lines.
+
+  This file shows which error types are supported:
+
+  Error Type Value	Error Description
+  ================	=================
+  0x00000001		Processor Correctable
+  0x00000002		Processor Uncorrectable non-fatal
+  0x00000004		Processor Uncorrectable fatal
+  0x00000008		Memory Correctable
+  0x00000010		Memory Uncorrectable non-fatal
+  0x00000020		Memory Uncorrectable fatal
+  0x00000040		PCI Express Correctable
+  0x00000080		PCI Express Uncorrectable fatal
+  0x00000100		PCI Express Uncorrectable non-fatal
+  0x00000200		Platform Correctable
+  0x00000400		Platform Uncorrectable non-fatal
+  0x00000800		Platform Uncorrectable fatal
+
+  The format of the file contents are as above, except present are only
+  the available error types.
 
 - error_type
-  This file is used to set the error type value. The error type value
-  is defined in "available_error_type" description.
+
+  Set the value of the error type being injected. Possible error types
+  are defined in the file available_error_type above.
 
 - error_inject
-  Write any integer to this file to trigger the error
-  injection. Before this, please specify all necessary error
-  parameters.
+
+  Write any integer to this file to trigger the error injection. Make
+  sure you have specified all necessary error parameters, i.e. this
+  write should be the last step when injecting errors.
 
 - flags
-  Present for kernel version 3.13 and above. Used to specify which
-  of param{1..4} are valid and should be used by BIOS during injection.
-  Value is a bitmask as specified in ACPI5.0 spec for the
+
+  Present for kernel versions 3.13 and above. Used to specify which
+  of param{1..4} are valid and should be used by the firmware during
+  injection. Value is a bitmask as specified in ACPI5.0 spec for the
   SET_ERROR_TYPE_WITH_ADDRESS data structure:
-	Bit 0 - Processor APIC field valid (see param3 below)
-	Bit 1 - Memory address and mask valid (param1 and param2)
-	Bit 2 - PCIe (seg,bus,dev,fn) valid (param4 below)
-  If set to zero, legacy behaviour is used where the type of injection
-  specifies just one bit set, and param1 is multiplexed.
+
+	Bit 0 - Processor APIC field valid (see param3 below).
+	Bit 1 - Memory address and mask valid (param1 and param2).
+	Bit 2 - PCIe (seg,bus,dev,fn) valid (see param4 below).
+
+  If set to zero, legacy behavior is mimicked where the type of
+  injection specifies just one bit set, and param1 is multiplexed.
 
 - param1
-  This file is used to set the first error parameter value. Effect of
-  parameter depends on error_type specified. For example, if error
-  type is memory related type, the param1 should be a valid physical
-  memory address. [Unless "flag" is set - see above]
+
+  This file is used to set the first error parameter value. Its effect
+  depends on the error type specified in error_type. For example, if
+  error type is memory related type, the param1 should be a valid
+  physical memory address. [Unless "flag" is set - see above]
 
 - param2
-  This file is used to set the second error parameter value. Effect of
-  parameter depends on error_type specified. For example, if error
-  type is memory related type, the param2 should be a physical memory
-  address mask. Linux requires page or narrower granularity, say,
-  0xfffffffffffff000.
+
+  Same use as param1 above. For example, if error type is of memory
+  related type, then param2 should be a physical memory address mask.
+  Linux requires page or narrower granularity, say, 0xfffffffffffff000.
 
 - param3
-  Used when the 0x1 bit is set in "flag" to specify the APIC id
+
+  Used when the 0x1 bit is set in "flags" to specify the APIC id
 
 - param4
-  Used when the 0x4 bit is set in "flag" to specify target PCIe device
+  Used when the 0x4 bit is set in "flags" to specify target PCIe device
 
 - notrigger
-  The EINJ mechanism is a two step process. First inject the error, then
-  perform some actions to trigger it. Setting "notrigger" to 1 skips the
-  trigger phase, which *may* allow the user to cause the error in some other
-  context by a simple access to the cpu, memory location, or device that is
-  the target of the error injection. Whether this actually works depends
-  on what operations the BIOS actually includes in the trigger phase.
-
-BIOS versions based in the ACPI 4.0 specification have limited options
-to control where the errors are injected.  Your BIOS may support an
-extension (enabled with the param_extension=1 module parameter, or
-boot command line einj.param_extension=1). This allows the address
-and mask for memory injections to be specified by the param1 and
-param2 files in apei/einj.
-
-BIOS versions using the ACPI 5.0 specification have more control over
-the target of the injection. For processor related errors (type 0x1,
-0x2 and 0x4) the APICID of the target should be provided using the
-param1 file in apei/einj. For memory errors (type 0x8, 0x10 and 0x20)
-the address is set using param1 with a mask in param2 (0x0 is equivalent
-to all ones). For PCI express errors (type 0x40, 0x80 and 0x100) the
-segment, bus, device and function are specified using param1:
+
+  The error injection mechanism is a two-step process. First inject the
+  error, then perform some actions to trigger it. Setting "notrigger"
+  to 1 skips the trigger phase, which *may* allow the user to cause the
+  error in some other context by a simple access to the CPU, memory
+  location, or device that is the target of the error injection. Whether
+  this actually works depends on what operations the BIOS actually
+  includes in the trigger phase.
+
+BIOS versions based on the ACPI 4.0 specification have limited options
+in controlling where the errors are injected. Your BIOS may support an
+extension (enabled with the param_extension=1 module parameter, or boot
+command line einj.param_extension=1). This allows the address and mask
+for memory injections to be specified by the param1 and param2 files in
+apei/einj.
+
+BIOS versions based on the ACPI 5.0 specification have more control over
+the target of the injection. For processor-related errors (type 0x1, 0x2
+and 0x4), you can set flags to 0x3 (param3 for bit 0, and param1 and
+param2 for bit 1) so that you have more information added to the error
+signature being injected. The actual data passed is this:
+
+	memory_address = param1;
+	memory_address_range = param2;
+	apicid = param3;
+	pcie_sbdf = param4;
+
+For memory errors (type 0x8, 0x10 and 0x20) the address is set using
+param1 with a mask in param2 (0x0 is equivalent to all ones). For PCI
+express errors (type 0x40, 0x80 and 0x100) the segment, bus, device and
+function are specified using param1:
 
          31     24 23    16 15    11 10      8  7        0
 	+-------------------------------------------------+
 	| segment |   bus  | device | function | reserved |
 	+-------------------------------------------------+
 
-An ACPI 5.0 BIOS may also allow vendor specific errors to be injected.
+Anyway, you get the idea, if there's doubt just take a look at the code
+in drivers/acpi/apei/einj.c.
+
+An ACPI 5.0 BIOS may also allow vendor-specific errors to be injected.
 In this case a file named vendor will contain identifying information
 from the BIOS that hopefully will allow an application wishing to use
-the vendor specific extension to tell that they are running on a BIOS
+the vendor-specific extension to tell that they are running on a BIOS
 that supports it. All vendor extensions have the 0x80000000 bit set in
 error_type. A file vendor_flags controls the interpretation of param1
 and param2 (1 = PROCESSOR, 2 = MEMORY, 4 = PCI). See your BIOS vendor
 documentation for details (and expect changes to this API if vendors
 creativity in using this feature expands beyond our expectations).
 
-Example:
+
+An error injection example:
+
 # cd /sys/kernel/debug/apei/einj
 # cat available_error_type		# See which errors can be injected
 0x00000002	Processor Uncorrectable non-fatal
 0x00000008	Memory Correctable
 0x00000010	Memory Uncorrectable non-fatal
 # echo 0x12345000 > param1		# Set memory address for injection
-# echo 0xfffffffffffff000 > param2	# Mask - anywhere in this page
+# echo $((-1 << 12)) > param2		# Mask 0xfffffffffffff000 - anywhere in this page
 # echo 0x8 > error_type			# Choose correctable memory error
 # echo 1 > error_inject			# Inject now
 
+You should see something like this in dmesg:
+
+[22715.830801] EDAC sbridge MC3: HANDLING MCE MEMORY ERROR
+[22715.834759] EDAC sbridge MC3: CPU 0: Machine Check Event: 0 Bank 7: 8c00004000010090
+[22715.834759] EDAC sbridge MC3: TSC 0
+[22715.834759] EDAC sbridge MC3: ADDR 12345000 EDAC sbridge MC3: MISC 144780c86
+[22715.834759] EDAC sbridge MC3: PROCESSOR 0:306e7 TIME 1422553404 SOCKET 0 APIC 0
+[22716.616173] EDAC MC3: 1 CE memory read error on CPU_SrcID#0_Channel#0_DIMM#0 (channel:0 slot:0 page:0x12345 offset:0x0 grain:32 syndrome:0x0 -  area:DRAM err_code:0001:0090 socket:0 channel_mask:1 rank:0)
 
 For more information about EINJ, please refer to ACPI specification
 version 4.0, section 17.5 and ACPI 5.0, section 18.6.

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);
 

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

arch/x86/kernel/cpu/mcheck/mce.c

@@ -59,7 +59,7 @@ 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);
 
@@ -88,9 +88,6 @@ 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).
@@ -624,8 +621,9 @@ 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;
@@ -648,7 +646,7 @@ 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.
@@ -681,8 +679,10 @@ 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.
@@ -696,6 +696,8 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 	 */
 
 	sync_core();
+
+	return error_logged;
 }
 EXPORT_SYMBOL_GPL(machine_check_poll);
 
@@ -815,7 +817,7 @@ 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.
@@ -828,7 +830,7 @@ 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
@@ -1260,7 +1262,7 @@ 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);
@@ -1270,49 +1272,57 @@ 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);
+
+	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());
+	}
 
-	return test_and_clear_bit(0, v);
+	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);
 }
 
 /*
@@ -1321,16 +1331,10 @@ 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);
 }
@@ -1631,7 +1635,7 @@ 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);

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);
 

arch/x86/kernel/cpu/mcheck/mce_intel.c

@@ -38,6 +38,15 @@
  */
 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);