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, 171 insertions, 0 deletions

diff --git a/drivers/acpi/wakeup.c b/drivers/acpi/wakeup.c
new file mode 100644
index 000000000..0cbee0f06
--- /dev/null
+++ b/drivers/acpi/wakeup.c
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * wakeup.c - support wakeup devices
+ * Copyright (C) 2004 Li Shaohua <shaohua.li@intel.com>
+ */
+
+#include <linux/init.h>
+#include <linux/acpi.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#include "internal.h"
+#include "sleep.h"
+
+struct acpi_wakeup_handler {
+	struct list_head list_node;
+	bool (*wakeup)(void *context);
+	void *context;
+};
+
+static LIST_HEAD(acpi_wakeup_handler_head);
+static DEFINE_MUTEX(acpi_wakeup_handler_mutex);
+
+/*
+ * We didn't lock acpi_device_lock in the file, because it invokes oops in
+ * suspend/resume and isn't really required as this is called in S-state. At
+ * that time, there is no device hotplug
+ **/
+
+/**
+ * acpi_enable_wakeup_devices - Enable wake-up device GPEs.
+ * @sleep_state: ACPI system sleep state.
+ *
+ * Enable wakeup device power of devices with the state.enable flag set and set
+ * the wakeup enable mask bits in the GPE registers that correspond to wakeup
+ * devices.
+ */
+void acpi_enable_wakeup_devices(u8 sleep_state)
+{
+	struct acpi_device *dev, *tmp;
+
+	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
+				 wakeup_list) {
+		if (!dev->wakeup.flags.valid
+		    || sleep_state > dev->wakeup.sleep_state
+		    || !(device_may_wakeup(&dev->dev)
+			 || dev->wakeup.prepare_count))
+			continue;
+
+		if (device_may_wakeup(&dev->dev))
+			acpi_enable_wakeup_device_power(dev, sleep_state);
+
+		/* The wake-up power should have been enabled already. */
+		acpi_set_gpe_wake_mask(dev->wakeup.gpe_device, dev->wakeup.gpe_number,
+				ACPI_GPE_ENABLE);
+	}
+}
+
+/**
+ * acpi_disable_wakeup_devices - Disable devices' wakeup capability.
+ * @sleep_state: ACPI system sleep state.
+ */
+void acpi_disable_wakeup_devices(u8 sleep_state)
+{
+	struct acpi_device *dev, *tmp;
+
+	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
+				 wakeup_list) {
+		if (!dev->wakeup.flags.valid
+		    || sleep_state > dev->wakeup.sleep_state
+		    || !(device_may_wakeup(&dev->dev)
+			 || dev->wakeup.prepare_count))
+			continue;
+
+		acpi_set_gpe_wake_mask(dev->wakeup.gpe_device, dev->wakeup.gpe_number,
+				ACPI_GPE_DISABLE);
+
+		if (device_may_wakeup(&dev->dev))
+			acpi_disable_wakeup_device_power(dev);
+	}
+}
+
+int __init acpi_wakeup_device_init(void)
+{
+	struct acpi_device *dev, *tmp;
+
+	mutex_lock(&acpi_device_lock);
+	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
+				 wakeup_list) {
+		if (device_can_wakeup(&dev->dev)) {
+			/* Button GPEs are supposed to be always enabled. */
+			acpi_enable_gpe(dev->wakeup.gpe_device,
+					dev->wakeup.gpe_number);
+			device_set_wakeup_enable(&dev->dev, true);
+		}
+	}
+	mutex_unlock(&acpi_device_lock);
+	return 0;
+}
+
+/**
+ * acpi_register_wakeup_handler - Register wakeup handler
+ * @wake_irq: The IRQ through which the device may receive wakeups
+ * @wakeup:   Wakeup-handler to call when the SCI has triggered a wakeup
+ * @context:  Context to pass to the handler when calling it
+ *
+ * Drivers which may share an IRQ with the SCI can use this to register
+ * a handler which returns true when the device they are managing wants
+ * to trigger a wakeup.
+ */
+int acpi_register_wakeup_handler(int wake_irq, bool (*wakeup)(void *context),
+				 void *context)
+{
+	struct acpi_wakeup_handler *handler;
+
+	/*
+	 * If the device is not sharing its IRQ with the SCI, there is no
+	 * need to register the handler.
+	 */
+	if (!acpi_sci_irq_valid() || wake_irq != acpi_sci_irq)
+		return 0;
+
+	handler = kmalloc_obj(*handler);
+	if (!handler)
+		return -ENOMEM;
+
+	handler->wakeup = wakeup;
+	handler->context = context;
+
+	mutex_lock(&acpi_wakeup_handler_mutex);
+	list_add(&handler->list_node, &acpi_wakeup_handler_head);
+	mutex_unlock(&acpi_wakeup_handler_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_register_wakeup_handler);
+
+/**
+ * acpi_unregister_wakeup_handler - Unregister wakeup handler
+ * @wakeup:   Wakeup-handler passed to acpi_register_wakeup_handler()
+ * @context:  Context passed to acpi_register_wakeup_handler()
+ */
+void acpi_unregister_wakeup_handler(bool (*wakeup)(void *context),
+				    void *context)
+{
+	struct acpi_wakeup_handler *handler;
+
+	mutex_lock(&acpi_wakeup_handler_mutex);
+	list_for_each_entry(handler, &acpi_wakeup_handler_head, list_node) {
+		if (handler->wakeup == wakeup && handler->context == context) {
+			list_del(&handler->list_node);
+			kfree(handler);
+			break;
+		}
+	}
+	mutex_unlock(&acpi_wakeup_handler_mutex);
+}
+EXPORT_SYMBOL_GPL(acpi_unregister_wakeup_handler);
+
+bool acpi_check_wakeup_handlers(void)
+{
+	struct acpi_wakeup_handler *handler;
+
+	/* No need to lock, nothing else is running when we're called. */
+	list_for_each_entry(handler, &acpi_wakeup_handler_head, list_node) {
+		if (handler->wakeup(handler->context))
+			return true;
+	}
+
+	return false;
+}