KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 244 insertions, 0 deletions

diff --git a/drivers/thermal/thermal_thresholds.c b/drivers/thermal/thermal_thresholds.c
new file mode 100644
index 000000000..970b8fd33
--- /dev/null
+++ b/drivers/thermal/thermal_thresholds.c
@@ -0,0 +1,244 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2024 Linaro Limited
+ *
+ * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
+ *
+ * Thermal thresholds
+ */
+#include <linux/list.h>
+#include <linux/list_sort.h>
+#include <linux/slab.h>
+
+#include "thermal_core.h"
+#include "thermal_thresholds.h"
+
+int thermal_thresholds_init(struct thermal_zone_device *tz)
+{
+	INIT_LIST_HEAD(&tz->user_thresholds);
+
+	return 0;
+}
+
+static void __thermal_thresholds_flush(struct thermal_zone_device *tz)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *entry, *tmp;
+
+	list_for_each_entry_safe(entry, tmp, thresholds, list_node) {
+		list_del(&entry->list_node);
+		kfree(entry);
+	}
+}
+
+void thermal_thresholds_flush(struct thermal_zone_device *tz)
+{
+	lockdep_assert_held(&tz->lock);
+
+	__thermal_thresholds_flush(tz);
+
+	thermal_notify_threshold_flush(tz);
+
+	__thermal_zone_device_update(tz, THERMAL_TZ_FLUSH_THRESHOLDS);
+}
+
+void thermal_thresholds_exit(struct thermal_zone_device *tz)
+{
+	__thermal_thresholds_flush(tz);
+}
+
+static int __thermal_thresholds_cmp(void *data,
+				    const struct list_head *l1,
+				    const struct list_head *l2)
+{
+	struct user_threshold *t1 = container_of(l1, struct user_threshold, list_node);
+	struct user_threshold *t2 = container_of(l2, struct user_threshold, list_node);
+
+	return t1->temperature - t2->temperature;
+}
+
+static struct user_threshold *__thermal_thresholds_find(const struct list_head *thresholds,
+							int temperature)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry(t, thresholds, list_node)
+		if (t->temperature == temperature)
+			return t;
+
+	return NULL;
+}
+
+static bool thermal_thresholds_handle_raising(struct list_head *thresholds, int temperature,
+					      int last_temperature)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry(t, thresholds, list_node) {
+
+		if (!(t->direction & THERMAL_THRESHOLD_WAY_UP))
+		    continue;
+
+		if (temperature >= t->temperature &&
+		    last_temperature < t->temperature)
+			return true;
+	}
+
+	return false;
+}
+
+static bool thermal_thresholds_handle_dropping(struct list_head *thresholds, int temperature,
+					       int last_temperature)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry_reverse(t, thresholds, list_node) {
+
+		if (!(t->direction & THERMAL_THRESHOLD_WAY_DOWN))
+		    continue;
+
+		if (temperature <= t->temperature &&
+		    last_temperature > t->temperature)
+			return true;
+	}
+
+	return false;
+}
+
+static void thermal_threshold_find_boundaries(struct list_head *thresholds, int temperature,
+					      int *low, int *high)
+{
+	struct user_threshold *t;
+
+	list_for_each_entry(t, thresholds, list_node) {
+		if (temperature < t->temperature &&
+		    (t->direction & THERMAL_THRESHOLD_WAY_UP) &&
+		    *high > t->temperature)
+			*high = t->temperature;
+	}
+
+	list_for_each_entry_reverse(t, thresholds, list_node) {
+		if (temperature > t->temperature &&
+		    (t->direction & THERMAL_THRESHOLD_WAY_DOWN) &&
+		    *low < t->temperature)
+			*low = t->temperature;
+	}
+}
+
+void thermal_thresholds_handle(struct thermal_zone_device *tz, int *low, int *high)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+
+	int temperature = tz->temperature;
+	int last_temperature = tz->last_temperature;
+
+	lockdep_assert_held(&tz->lock);
+
+	thermal_threshold_find_boundaries(thresholds, temperature, low, high);
+
+	/*
+	 * We need a second update in order to detect a threshold being crossed
+	 */
+	if (last_temperature == THERMAL_TEMP_INVALID)
+		return;
+
+	/*
+	 * The temperature is stable, so obviously we can not have
+	 * crossed a threshold.
+	 */
+	if (last_temperature == temperature)
+		return;
+
+	/*
+	 * Since last update the temperature:
+	 * - increased : thresholds are crossed the way up
+	 * - decreased : thresholds are crossed the way down
+	 */
+	if (temperature > last_temperature) {
+		if (thermal_thresholds_handle_raising(thresholds,
+						      temperature, last_temperature))
+			thermal_notify_threshold_up(tz);
+	} else {
+		if (thermal_thresholds_handle_dropping(thresholds,
+						       temperature, last_temperature))
+			thermal_notify_threshold_down(tz);
+	}
+}
+
+int thermal_thresholds_add(struct thermal_zone_device *tz,
+			   int temperature, int direction)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *t;
+
+	lockdep_assert_held(&tz->lock);
+
+	t = __thermal_thresholds_find(thresholds, temperature);
+	if (t) {
+		if (t->direction == direction)
+			return -EEXIST;
+
+		t->direction |= direction;
+	} else {
+
+		t = kmalloc_obj(*t);
+		if (!t)
+			return -ENOMEM;
+
+		INIT_LIST_HEAD(&t->list_node);
+		t->temperature = temperature;
+		t->direction = direction;
+		list_add(&t->list_node, thresholds);
+		list_sort(NULL, thresholds, __thermal_thresholds_cmp);
+	}
+
+	thermal_notify_threshold_add(tz, temperature, direction);
+
+	__thermal_zone_device_update(tz, THERMAL_TZ_ADD_THRESHOLD);
+
+	return 0;
+}
+
+int thermal_thresholds_delete(struct thermal_zone_device *tz,
+			      int temperature, int direction)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *t;
+
+	lockdep_assert_held(&tz->lock);
+
+	t = __thermal_thresholds_find(thresholds, temperature);
+	if (!t)
+		return -ENOENT;
+
+	if (t->direction == direction) {
+		list_del(&t->list_node);
+		kfree(t);
+	} else {
+		t->direction &= ~direction;
+	}
+
+	thermal_notify_threshold_delete(tz, temperature, direction);
+
+	__thermal_zone_device_update(tz, THERMAL_TZ_DEL_THRESHOLD);
+
+	return 0;
+}
+
+int thermal_thresholds_for_each(struct thermal_zone_device *tz,
+				int (*cb)(struct user_threshold *, void *arg), void *arg)
+{
+	struct list_head *thresholds = &tz->user_thresholds;
+	struct user_threshold *entry;
+	int ret;
+
+	guard(thermal_zone)(tz);
+
+	list_for_each_entry(entry, thresholds, list_node) {
+		ret = cb(entry, arg);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}