1 files changed, 122 insertions, 88 deletions

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 88e4f3ff0cb8..5d545806d930 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -1,7 +1,11 @@
 // SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2017-2019 Borislav Petkov, SUSE Labs.
+ */
 #include <linux/mm.h>
 #include <linux/gfp.h>
 #include <linux/kernel.h>
+#include <linux/workqueue.h>
 
 #include <asm/mce.h>
 
@@ -36,9 +40,9 @@
  * 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
@@ -121,18 +125,14 @@ static DEFINE_MUTEX(ce_mutex);
 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.
- */
+static u64 action_threshold = COUNT_MASK;
 
-#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 +160,21 @@ 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);
 }
 
 /*
@@ -183,32 +184,38 @@ 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;
 }
 
@@ -272,11 +279,39 @@ 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;
 
 	/*
@@ -290,6 +325,7 @@ 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));
 
@@ -302,24 +338,17 @@ 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 >= action_threshold) {
 		u64 pfn = ca->array[to] >> PAGE_SHIFT;
 
 		if (!pfn_valid(pfn)) {
@@ -334,20 +363,21 @@ 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)
 		do_spring_cleaning(ca);
 
+	WARN_ON_ONCE(sanity_check(ca));
+
 unlock:
 	mutex_unlock(&ce_mutex);
 
@@ -365,45 +395,48 @@ 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");
 
 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;
+	*(u64 *)data   = val;
+	decay_interval = val;
+
+	cec_mod_work(decay_interval);
 
-	cec_mod_timer(&cec_timer, timer_interval);
 	return 0;
 }
 DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_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, u64_get, count_threshold_set, "%lld\n");
+DEFINE_DEBUGFS_ATTRIBUTE(action_threshold_ops, u64_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;
-	u64 prev = 0;
 	int i;
 
 	mutex_lock(&ce_mutex);
@@ -412,11 +445,8 @@ 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]));
-
-		WARN_ON(prev > this);
-
-		prev = this;
+		seq_printf(m, " %3d: [%016llx|%s|%03llx]\n",
+			   i, this, bins[DECAY(ca->array[i])], COUNT(ca->array[i]));
 	}
 
 	seq_printf(m, "}\n");
@@ -426,10 +456,10 @@ 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);
+	seq_printf(m, "Action threshold: %lld\n", action_threshold);
 
 	mutex_unlock(&ce_mutex);
 
@@ -459,33 +489,35 @@ 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");
+	decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d,
+				    &decay_interval, &decay_interval_ops);
+	if (!decay) {
+		pr_warn("Error creating decay_interval 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");
+	count = debugfs_create_file("action_threshold", S_IRUSR | S_IWUSR, d,
+				    &action_threshold, &action_threshold_ops);
+	if (!count) {
+		pr_warn("Error creating action_threshold debugfs node!\n");
 		goto err;
 	}
 
-	decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d,
-				    &timer_interval, &decay_interval_ops);
-	if (!decay) {
-		pr_warn("Error creating decay_interval debugfs node!\n");
+	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;
 	}
 
-	count = debugfs_create_file("count_threshold", S_IRUSR | S_IWUSR, d,
-				    &count_threshold, &count_threshold_ops);
-	if (!count) {
-		pr_warn("Error creating count_threshold debugfs node!\n");
+	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;
 
 err:
@@ -505,11 +537,13 @@ void __init cec_init(void)
 		return;
 	}
 
-	if (create_debugfs_nodes())
+	if (create_debugfs_nodes()) {
+		free_page((unsigned long)ce_arr.array);
 		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");
 }