[PATCH 00/11] RAS/CEC: Fixes and cleanups

[PATCH 00/11] RAS/CEC: Fixes and cleanups

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Hi all,

here are a bunch of fixes and cleanups to the correctable errors
collector which we've been working on in the recent weeks.

Thx.

Borislav Petkov (9):
  RAS/CEC: Fix binary search function
  RAS/CEC: Fix pfn insertion
  RAS/CEC: Check count_threshold unconditionally
  RAS/CEC: Do not set decay value on error
  RAS/CEC: Fix potential memory leak
  RAS/CEC: Sanity-check array on every insertion
  RAS/CEC: Rename count_threshold to action_threshold
  RAS/CEC: Dump the different array element sections
  RAS/CEC: Add copyright

Cong Wang (1):
  RAS/CEC: Convert the timer callback to a workqueue

Tony Luck (1):
  RAS/CEC: Add CONFIG_RAS_CEC_DEBUG and move CEC debug features there

 arch/x86/ras/Kconfig |  10 ++
 drivers/ras/cec.c    | 216 +++++++++++++++++++++++++------------------
 2 files changed, 135 insertions(+), 91 deletions(-)

-- 
2.21.0

[PATCH 01/11] RAS/CEC: Fix binary search function

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Switch to using Donald Knuth's binary search algorithm (The Art of
Computer Programming, vol. 3, section 6.2.1). This should've been done
from the very beginning but the author must've been smoking something
very potent at the time.

The problem with the current one was that it would return the wrong
element index in certain situations:

  https://lkml.kernel.org/r/CAM_iQpVd02zkVJ846cj-Fg1yUNuz6tY5q1Vpj4LrXmE06dPYYg@mail.gmail.com

and the noodling code after the loop was fishy at best.

So switch to using Knuth's binary search. The final result is much
cleaner and straightforward.

Fixes: 011d82611172 ("RAS: Add a Corrected Errors Collector")
Reported-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: <stable@vger.kernel.org>
---
 drivers/ras/cec.c | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 88e4f3ff0cb8..dbfe3e61d2c2 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -183,32 +183,38 @@ static void cec_timer_fn(struct timer_list *unused)
  */
 static int __find_elem(struct ce_array *ca, u64 pfn, unsigned int *to)
 {
+	int min = 0, max = ca->n - 1;
 	u64 this_pfn;
-	int min = 0, max = ca->n;
 
-	while (min < max) {
-		int tmp = (max + min) >> 1;
+	while (min <= max) {
+		int i = (min + max) >> 1;
 
-		this_pfn = PFN(ca->array[tmp]);
+		this_pfn = PFN(ca->array[i]);
 
 		if (this_pfn < pfn)
-			min = tmp + 1;
+			min = i + 1;
 		else if (this_pfn > pfn)
-			max = tmp;
-		else {
-			min = tmp;
-			break;
+			max = i - 1;
+		else if (this_pfn == pfn) {
+			if (to)
+				*to = i;
+
+			return i;
 		}
 	}
 
+	/*
+	 * When the loop terminates without finding @pfn, min has the index of
+	 * the element slot where the new @pfn should be inserted. The loop
+	 * terminates when min > max, which means the min index points to the
+	 * bigger element while the max index to the smaller element, in-between
+	 * which the new @pfn belongs to.
+	 *
+	 * For more details, see exercise 1, Section 6.2.1 in TAOCP, vol. 3.
+	 */
 	if (to)
 		*to = min;
 
-	this_pfn = PFN(ca->array[min]);
-
-	if (this_pfn == pfn)
-		return min;
-
 	return -ENOKEY;
 }
 
-- 
2.21.0

[PATCH 02/11] RAS/CEC: Convert the timer callback to a workqueue

[Borislav Petkov]

From: Cong Wang <xiyou.wangcong@gmail.com>

cec_timer_fn() is a timer callback which reads ce_arr.array[] and
updates its decay values. However, it runs in interrupt context and the
mutex protection the CEC uses for that array, is inadequate. Convert the
used timer to a workqueue to keep the tasks the CEC performs preemptible
and thus low-prio.

 [ bp: Rewrite commit message.
   s/timer/decay/gi to make it agnostic as to what facility is used. ]

Fixes: 011d82611172 ("RAS: Add a Corrected Errors Collector")
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20190416213351.28999-2-xiyou.wangcong@gmail.com
---
 drivers/ras/cec.c | 46 ++++++++++++++++++++++------------------------
 1 file changed, 22 insertions(+), 24 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index dbfe3e61d2c2..673f8a128397 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -2,6 +2,7 @@
 #include <linux/mm.h>
 #include <linux/gfp.h>
 #include <linux/kernel.h>
+#include <linux/workqueue.h>
 
 #include <asm/mce.h>
 
@@ -123,16 +124,12 @@ static u64 dfs_pfn;
 /* Amount of errors after which we offline */
 static unsigned int count_threshold = COUNT_MASK;
 
-/*
- * The timer "decays" element count each timer_interval which is 24hrs by
- * default.
- */
-
-#define CEC_TIMER_DEFAULT_INTERVAL	24 * 60 * 60	/* 24 hrs */
-#define CEC_TIMER_MIN_INTERVAL		 1 * 60 * 60	/* 1h */
-#define CEC_TIMER_MAX_INTERVAL	   30 *	24 * 60 * 60	/* one month */
-static struct timer_list cec_timer;
-static u64 timer_interval = CEC_TIMER_DEFAULT_INTERVAL;
+/* Each element "decays" each decay_interval which is 24hrs by default. */
+#define CEC_DECAY_DEFAULT_INTERVAL	24 * 60 * 60	/* 24 hrs */
+#define CEC_DECAY_MIN_INTERVAL		 1 * 60 * 60	/* 1h */
+#define CEC_DECAY_MAX_INTERVAL	   30 *	24 * 60 * 60	/* one month */
+static struct delayed_work cec_work;
+static u64 decay_interval = CEC_DECAY_DEFAULT_INTERVAL;
 
 /*
  * Decrement decay value. We're using DECAY_BITS bits to denote decay of an
@@ -160,20 +157,21 @@ static void do_spring_cleaning(struct ce_array *ca)
 /*
  * @interval in seconds
  */
-static void cec_mod_timer(struct timer_list *t, unsigned long interval)
+static void cec_mod_work(unsigned long interval)
 {
 	unsigned long iv;
 
-	iv = interval * HZ + jiffies;
-
-	mod_timer(t, round_jiffies(iv));
+	iv = interval * HZ;
+	mod_delayed_work(system_wq, &cec_work, round_jiffies(iv));
 }
 
-static void cec_timer_fn(struct timer_list *unused)
+static void cec_work_fn(struct work_struct *work)
 {
+	mutex_lock(&ce_mutex);
 	do_spring_cleaning(&ce_arr);
+	mutex_unlock(&ce_mutex);
 
-	cec_mod_timer(&cec_timer, timer_interval);
+	cec_mod_work(decay_interval);
 }
 
 /*
@@ -380,15 +378,15 @@ static int decay_interval_set(void *data, u64 val)
 {
 	*(u64 *)data = val;
 
-	if (val < CEC_TIMER_MIN_INTERVAL)
+	if (val < CEC_DECAY_MIN_INTERVAL)
 		return -EINVAL;
 
-	if (val > CEC_TIMER_MAX_INTERVAL)
+	if (val > CEC_DECAY_MAX_INTERVAL)
 		return -EINVAL;
 
-	timer_interval = val;
+	decay_interval = val;
 
-	cec_mod_timer(&cec_timer, timer_interval);
+	cec_mod_work(decay_interval);
 	return 0;
 }
 DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_get, decay_interval_set, "%lld\n");
@@ -432,7 +430,7 @@ static int array_dump(struct seq_file *m, void *v)
 
 	seq_printf(m, "Flags: 0x%x\n", ca->flags);
 
-	seq_printf(m, "Timer interval: %lld seconds\n", timer_interval);
+	seq_printf(m, "Decay interval: %lld seconds\n", decay_interval);
 	seq_printf(m, "Decays: %lld\n", ca->decays_done);
 
 	seq_printf(m, "Action threshold: %d\n", count_threshold);
@@ -478,7 +476,7 @@ static int __init create_debugfs_nodes(void)
 	}
 
 	decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d,
-				    &timer_interval, &decay_interval_ops);
+				    &decay_interval, &decay_interval_ops);
 	if (!decay) {
 		pr_warn("Error creating decay_interval debugfs node!\n");
 		goto err;
@@ -514,8 +512,8 @@ void __init cec_init(void)
 	if (create_debugfs_nodes())
 		return;
 
-	timer_setup(&cec_timer, cec_timer_fn, 0);
-	cec_mod_timer(&cec_timer, CEC_TIMER_DEFAULT_INTERVAL);
+	INIT_DELAYED_WORK(&cec_work, cec_work_fn);
+	schedule_delayed_work(&cec_work, CEC_DECAY_DEFAULT_INTERVAL);
 
 	pr_info("Correctable Errors collector initialized.\n");
 }
-- 
2.21.0

[PATCH 03/11] RAS/CEC: Fix pfn insertion

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

When inserting random PFNs for debugging the CEC through
(debugfs)/ras/cec/pfn, depending on the return value of pfn_set(),
multiple values get inserted per a single write.

That is because simple_attr_write() interprets a retval of 0 as
success and claims the whole input. However, pfn_set() returns the
cec_add_elem() value, which, if > 0 and smaller than the whole input
length, makes glibc continue issuing the write syscall until there's
input left:

  pfn_set
  simple_attr_write
  debugfs_attr_write
  full_proxy_write
  vfs_write
  ksys_write
  do_syscall_64
  entry_SYSCALL_64_after_hwframe

leading to those repeated calls.

Return 0 to fix that.

Rename u64_get() to pfn_get() while at it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
---
 drivers/ras/cec.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 673f8a128397..1275907ff21c 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -358,7 +358,7 @@ int cec_add_elem(u64 pfn)
 	return ret;
 }
 
-static int u64_get(void *data, u64 *val)
+static int pfn_get(void *data, u64 *val)
 {
 	*val = *(u64 *)data;
 
@@ -369,10 +369,12 @@ static int pfn_set(void *data, u64 val)
 {
 	*(u64 *)data = val;
 
-	return cec_add_elem(val);
+	cec_add_elem(val);
+
+	return 0;
 }
 
-DEFINE_DEBUGFS_ATTRIBUTE(pfn_ops, u64_get, pfn_set, "0x%llx\n");
+DEFINE_DEBUGFS_ATTRIBUTE(pfn_ops, pfn_get, pfn_set, "0x%llx\n");
 
 static int decay_interval_set(void *data, u64 val)
 {
@@ -389,7 +391,7 @@ static int decay_interval_set(void *data, u64 val)
 	cec_mod_work(decay_interval);
 	return 0;
 }
-DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_get, decay_interval_set, "%lld\n");
+DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, pfn_get, decay_interval_set, "%lld\n");
 
 static int count_threshold_set(void *data, u64 val)
 {
@@ -402,7 +404,7 @@ static int count_threshold_set(void *data, u64 val)
 
 	return 0;
 }
-DEFINE_DEBUGFS_ATTRIBUTE(count_threshold_ops, u64_get, count_threshold_set, "%lld\n");
+DEFINE_DEBUGFS_ATTRIBUTE(count_threshold_ops, pfn_get, count_threshold_set, "%lld\n");
 
 static int array_dump(struct seq_file *m, void *v)
 {
-- 
2.21.0

[PATCH 04/11] RAS/CEC: Check count_threshold unconditionally

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

The count_threshold should be checked unconditionally, after insertion
too, so that a count_threshold value of 1 can cause an immediate
offlining. I.e., offline the page on the *first* error encountered.

Add comments to make it clear what cec_add_elem() does, while at it.

Reported-by: WANG Chao <chao.wang@ucloud.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac@vger.kernel.org
Link: https://lkml.kernel.org/r/20190418034115.75954-3-chao.wang@ucloud.cn
---
 drivers/ras/cec.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 1275907ff21c..73216b7f67be 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -294,6 +294,7 @@ int cec_add_elem(u64 pfn)
 
 	ca->ces_entered++;
 
+	/* Array full, free the LRU slot. */
 	if (ca->n == MAX_ELEMS)
 		WARN_ON(!del_lru_elem_unlocked(ca));
 
@@ -306,24 +307,17 @@ int cec_add_elem(u64 pfn)
 			(void *)&ca->array[to],
 			(ca->n - to) * sizeof(u64));
 
-		ca->array[to] = (pfn << PAGE_SHIFT) |
-				(DECAY_MASK << COUNT_BITS) | 1;
-
+		ca->array[to] = pfn << PAGE_SHIFT;
 		ca->n++;
-
-		ret = 0;
-
-		goto decay;
 	}
 
-	count = COUNT(ca->array[to]);
-
-	if (count < count_threshold) {
-		ca->array[to] |= (DECAY_MASK << COUNT_BITS);
-		ca->array[to]++;
+	/* Add/refresh element generation and increment count */
+	ca->array[to] |= DECAY_MASK << COUNT_BITS;
+	ca->array[to]++;
 
-		ret = 0;
-	} else {
+	/* Check action threshold and soft-offline, if reached. */
+	count = COUNT(ca->array[to]);
+	if (count >= count_threshold) {
 		u64 pfn = ca->array[to] >> PAGE_SHIFT;
 
 		if (!pfn_valid(pfn)) {
@@ -338,15 +332,14 @@ int cec_add_elem(u64 pfn)
 		del_elem(ca, to);
 
 		/*
-		 * Return a >0 value to denote that we've reached the offlining
-		 * threshold.
+		 * Return a >0 value to callers, to denote that we've reached
+		 * the offlining threshold.
 		 */
 		ret = 1;
 
 		goto unlock;
 	}
 
-decay:
 	ca->decay_count++;
 
 	if (ca->decay_count >= CLEAN_ELEMS)
-- 
2.21.0

[PATCH 05/11] RAS/CEC: Do not set decay value on error

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

When the value requested doesn't match the allowed (min,max) range,
the @data buffer should not be modified with the invalid value because
reading "decay_interval" shows it otherwise.

Move the data write after the check.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
---
 drivers/ras/cec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 73216b7f67be..667a126f39f1 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -371,17 +371,17 @@ DEFINE_DEBUGFS_ATTRIBUTE(pfn_ops, pfn_get, pfn_set, "0x%llx\n");
 
 static int decay_interval_set(void *data, u64 val)
 {
-	*(u64 *)data = val;
-
 	if (val < CEC_DECAY_MIN_INTERVAL)
 		return -EINVAL;
 
 	if (val > CEC_DECAY_MAX_INTERVAL)
 		return -EINVAL;
 
+	*(u64 *)data   = val;
 	decay_interval = val;
 
 	cec_mod_work(decay_interval);
+
 	return 0;
 }
 DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, pfn_get, decay_interval_set, "%lld\n");
-- 
2.21.0

[PATCH 06/11] RAS/CEC: Fix potential memory leak

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Free the array page if a failure is encountered while creating the
debugfs nodes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
---
 drivers/ras/cec.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 667a126f39f1..8a04b9864192 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -504,8 +504,10 @@ void __init cec_init(void)
 		return;
 	}
 
-	if (create_debugfs_nodes())
+	if (create_debugfs_nodes()) {
+		free_page((unsigned long)ce_arr.array);
 		return;
+	}
 
 	INIT_DELAYED_WORK(&cec_work, cec_work_fn);
 	schedule_delayed_work(&cec_work, CEC_DECAY_DEFAULT_INTERVAL);
-- 
2.21.0

[PATCH 07/11] RAS/CEC: Sanity-check array on every insertion

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Check the elements order in the array after every insertion.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
---
 drivers/ras/cec.c | 37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 8a04b9864192..2c92a70fa2f0 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -276,11 +276,39 @@ static u64 __maybe_unused del_lru_elem(void)
 	return pfn;
 }
 
+static bool sanity_check(struct ce_array *ca)
+{
+	bool ret = false;
+	u64 prev = 0;
+	int i;
+
+	for (i = 0; i < ca->n; i++) {
+		u64 this = PFN(ca->array[i]);
+
+		if (WARN(prev > this, "prev: 0x%016llx <-> this: 0x%016llx\n", prev, this))
+			ret = true;
+
+		prev = this;
+	}
+
+	if (!ret)
+		return ret;
+
+	pr_info("Sanity check dump:\n{ n: %d\n", ca->n);
+	for (i = 0; i < ca->n; i++) {
+		u64 this = PFN(ca->array[i]);
+
+		pr_info(" %03d: [%016llx|%03llx]\n", i, this, FULL_COUNT(ca->array[i]));
+	}
+	pr_info("}\n");
+
+	return ret;
+}
 
 int cec_add_elem(u64 pfn)
 {
 	struct ce_array *ca = &ce_arr;
-	unsigned int to;
+	unsigned int to = 0;
 	int count, ret = 0;
 
 	/*
@@ -345,6 +373,8 @@ int cec_add_elem(u64 pfn)
 	if (ca->decay_count >= CLEAN_ELEMS)
 		do_spring_cleaning(ca);
 
+	WARN_ON_ONCE(sanity_check(ca));
+
 unlock:
 	mutex_unlock(&ce_mutex);
 
@@ -402,7 +432,6 @@ DEFINE_DEBUGFS_ATTRIBUTE(count_threshold_ops, pfn_get, count_threshold_set, "%ll
 static int array_dump(struct seq_file *m, void *v)
 {
 	struct ce_array *ca = &ce_arr;
-	u64 prev = 0;
 	int i;
 
 	mutex_lock(&ce_mutex);
@@ -412,10 +441,6 @@ static int array_dump(struct seq_file *m, void *v)
 		u64 this = PFN(ca->array[i]);
 
 		seq_printf(m, " %03d: [%016llx|%03llx]\n", i, this, FULL_COUNT(ca->array[i]));
-
-		WARN_ON(prev > this);
-
-		prev = this;
 	}
 
 	seq_printf(m, "}\n");
-- 
2.21.0

[PATCH 08/11] RAS/CEC: Rename count_threshold to action_threshold

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

... which is the better, more-fitting name anyway.

Tony:
 - make action_threshold u64 due to debugfs accessors expecting u64.
 - rename the remaining: s/count_threshold/action_threshold/g

Co-developed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: linux-edac <linux-edac@vger.kernel.org>
---
 drivers/ras/cec.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 2c92a70fa2f0..1cbc1ed82afe 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -37,9 +37,9 @@
  * thus emulate an an LRU-like behavior when deleting elements to free up space
  * in the page.
  *
- * When an element reaches it's max count of count_threshold, we try to poison
- * it by assuming that errors triggered count_threshold times in a single page
- * are excessive and that page shouldn't be used anymore. count_threshold is
+ * When an element reaches it's max count of action_threshold, we try to poison
+ * it by assuming that errors triggered action_threshold times in a single page
+ * are excessive and that page shouldn't be used anymore. action_threshold is
  * initialized to COUNT_MASK which is the maximum.
  *
  * That error event entry causes cec_add_elem() to return !0 value and thus
@@ -122,7 +122,7 @@ static DEFINE_MUTEX(ce_mutex);
 static u64 dfs_pfn;
 
 /* Amount of errors after which we offline */
-static unsigned int count_threshold = COUNT_MASK;
+static u64 action_threshold = COUNT_MASK;
 
 /* Each element "decays" each decay_interval which is 24hrs by default. */
 #define CEC_DECAY_DEFAULT_INTERVAL	24 * 60 * 60	/* 24 hrs */
@@ -345,7 +345,7 @@ int cec_add_elem(u64 pfn)
 
 	/* Check action threshold and soft-offline, if reached. */
 	count = COUNT(ca->array[to]);
-	if (count >= count_threshold) {
+	if (count >= action_threshold) {
 		u64 pfn = ca->array[to] >> PAGE_SHIFT;
 
 		if (!pfn_valid(pfn)) {
@@ -416,18 +416,18 @@ static int decay_interval_set(void *data, u64 val)
 }
 DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, pfn_get, decay_interval_set, "%lld\n");
 
-static int count_threshold_set(void *data, u64 val)
+static int action_threshold_set(void *data, u64 val)
 {
 	*(u64 *)data = val;
 
 	if (val > COUNT_MASK)
 		val = COUNT_MASK;
 
-	count_threshold = val;
+	action_threshold = val;
 
 	return 0;
 }
-DEFINE_DEBUGFS_ATTRIBUTE(count_threshold_ops, pfn_get, count_threshold_set, "%lld\n");
+DEFINE_DEBUGFS_ATTRIBUTE(action_threshold_ops, pfn_get, action_threshold_set, "%lld\n");
 
 static int array_dump(struct seq_file *m, void *v)
 {
@@ -453,7 +453,7 @@ static int array_dump(struct seq_file *m, void *v)
 	seq_printf(m, "Decay interval: %lld seconds\n", decay_interval);
 	seq_printf(m, "Decays: %lld\n", ca->decays_done);
 
-	seq_printf(m, "Action threshold: %d\n", count_threshold);
+	seq_printf(m, "Action threshold: %lld\n", action_threshold);
 
 	mutex_unlock(&ce_mutex);
 
@@ -502,10 +502,10 @@ static int __init create_debugfs_nodes(void)
 		goto err;
 	}
 
-	count = debugfs_create_file("count_threshold", S_IRUSR | S_IWUSR, d,
-				    &count_threshold, &count_threshold_ops);
+	count = debugfs_create_file("action_threshold", S_IRUSR | S_IWUSR, d,
+				    &action_threshold, &action_threshold_ops);
 	if (!count) {
-		pr_warn("Error creating count_threshold debugfs node!\n");
+		pr_warn("Error creating action_threshold debugfs node!\n");
 		goto err;
 	}
 
-- 
2.21.0

[PATCH 09/11] RAS/CEC: Dump the different array element sections

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

When dumping the array elements, print them in the following format:

  [ PFN | generation in binary | count ]

to be perfectly clear what all those sections are.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
---
 drivers/ras/cec.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 1cbc1ed82afe..71f3e14c35d8 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -429,6 +429,8 @@ static int action_threshold_set(void *data, u64 val)
 }
 DEFINE_DEBUGFS_ATTRIBUTE(action_threshold_ops, pfn_get, action_threshold_set, "%lld\n");
 
+static const char * const bins[] = { "00", "01", "10", "11" };
+
 static int array_dump(struct seq_file *m, void *v)
 {
 	struct ce_array *ca = &ce_arr;
@@ -440,7 +442,8 @@ static int array_dump(struct seq_file *m, void *v)
 	for (i = 0; i < ca->n; i++) {
 		u64 this = PFN(ca->array[i]);
 
-		seq_printf(m, " %03d: [%016llx|%03llx]\n", i, this, FULL_COUNT(ca->array[i]));
+		seq_printf(m, " %3d: [%016llx|%s|%03llx]\n",
+			   i, this, bins[DECAY(ca->array[i])], COUNT(ca->array[i]));
 	}
 
 	seq_printf(m, "}\n");
-- 
2.21.0

[PATCH 10/11] RAS/CEC: Add CONFIG_RAS_CEC_DEBUG and move CEC debug features there

[Borislav Petkov]

From: Tony Luck <tony.luck@intel.com>

The pfn and array files in (debugfs)/ras/cec are intended for debugging
the CEC code itself. They are not needed on production systems, so the
default setting for this CONFIG option is "n".

 [ bp: Have it with less ifdeffery by using IS_ENABLED(). ]

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/ras/Kconfig | 10 ++++++++++
 drivers/ras/cec.c    | 26 ++++++++++++++------------
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/arch/x86/ras/Kconfig b/arch/x86/ras/Kconfig
index a9c3db125222..9ad6842de4b4 100644
--- a/arch/x86/ras/Kconfig
+++ b/arch/x86/ras/Kconfig
@@ -11,3 +11,13 @@ config RAS_CEC
 
 	  Bear in mind that this is absolutely useless if your platform doesn't
 	  have ECC DIMMs and doesn't have DRAM ECC checking enabled in the BIOS.
+
+config RAS_CEC_DEBUG
+	bool "CEC debugging machinery"
+	default n
+	depends on RAS_CEC
+	help
+	  Add extra files to (debugfs)/ras/cec to test the correctable error
+	  collector feature. "pfn" is a writable file that allows user to
+	  simulate an error in a particular page frame. "array" is a read-only
+	  file that dumps out the current state of all pages logged so far.
diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 71f3e14c35d8..c4505c0893a7 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -486,18 +486,6 @@ static int __init create_debugfs_nodes(void)
 		return -1;
 	}
 
-	pfn = debugfs_create_file("pfn", S_IRUSR | S_IWUSR, d, &dfs_pfn, &pfn_ops);
-	if (!pfn) {
-		pr_warn("Error creating pfn debugfs node!\n");
-		goto err;
-	}
-
-	array = debugfs_create_file("array", S_IRUSR, d, NULL, &array_ops);
-	if (!array) {
-		pr_warn("Error creating array debugfs node!\n");
-		goto err;
-	}
-
 	decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d,
 				    &decay_interval, &decay_interval_ops);
 	if (!decay) {
@@ -512,6 +500,20 @@ static int __init create_debugfs_nodes(void)
 		goto err;
 	}
 
+	if (!IS_ENABLED(CONFIG_RAS_CEC_DEBUG))
+		return 0;
+
+	pfn = debugfs_create_file("pfn", S_IRUSR | S_IWUSR, d, &dfs_pfn, &pfn_ops);
+	if (!pfn) {
+		pr_warn("Error creating pfn debugfs node!\n");
+		goto err;
+	}
+
+	array = debugfs_create_file("array", S_IRUSR, d, NULL, &array_ops);
+	if (!array) {
+		pr_warn("Error creating array debugfs node!\n");
+		goto err;
+	}
 
 	return 0;
 
-- 
2.21.0

[PATCH 11/11] RAS/CEC: Add copyright

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 drivers/ras/cec.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index c4505c0893a7..5402e907ae7a 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -1,4 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2017- Borislav Petkov, SUSE Labs.
+ */
 #include <linux/mm.h>
 #include <linux/gfp.h>
 #include <linux/kernel.h>
-- 
2.21.0