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, 90 insertions, 0 deletions

diff --git a/drivers/acpi/hed.c b/drivers/acpi/hed.c
new file mode 100644
index 000000000..48562f53d
--- /dev/null
+++ b/drivers/acpi/hed.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ACPI Hardware Error Device (PNP0C33) Driver
+ *
+ * Copyright (C) 2010, Intel Corp.
+ *	Author: Huang Ying <ying.huang@intel.com>
+ *
+ * ACPI Hardware Error Device is used to report some hardware errors
+ * notified via SCI, mainly the corrected errors.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+#include <acpi/hed.h>
+
+static const struct acpi_device_id acpi_hed_ids[] = {
+	{"PNP0C33", 0},
+	{"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, acpi_hed_ids);
+
+static bool hed_present;
+
+static BLOCKING_NOTIFIER_HEAD(acpi_hed_notify_list);
+
+int register_acpi_hed_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&acpi_hed_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(register_acpi_hed_notifier);
+
+void unregister_acpi_hed_notifier(struct notifier_block *nb)
+{
+	blocking_notifier_chain_unregister(&acpi_hed_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_acpi_hed_notifier);
+
+/*
+ * SCI to report hardware error is forwarded to the listeners of HED,
+ * it is used by HEST Generic Hardware Error Source with notify type
+ * SCI.
+ */
+static void acpi_hed_notify(acpi_handle handle, u32 event, void *data)
+{
+	blocking_notifier_call_chain(&acpi_hed_notify_list, 0, NULL);
+}
+
+static int acpi_hed_probe(struct platform_device *pdev)
+{
+	int err;
+
+	/* Only one hardware error device */
+	if (hed_present)
+		return -EINVAL;
+
+	err = devm_acpi_install_notify_handler(&pdev->dev, ACPI_DEVICE_NOTIFY,
+					       acpi_hed_notify, NULL);
+	if (err)
+		return err;
+
+	hed_present = true;
+	return 0;
+}
+
+static void acpi_hed_remove(struct platform_device *pdev)
+{
+	hed_present = false;
+}
+
+static struct platform_driver acpi_hed_driver = {
+	.probe = acpi_hed_probe,
+	.remove = acpi_hed_remove,
+	.driver = {
+		.name = "acpi-hardware-error-device",
+		.acpi_match_table = acpi_hed_ids,
+	},
+};
+
+static int __init acpi_hed_driver_init(void)
+{
+	return platform_driver_register(&acpi_hed_driver);
+}
+subsys_initcall(acpi_hed_driver_init);
+
+MODULE_AUTHOR("Huang Ying");
+MODULE_DESCRIPTION("ACPI Hardware Error Device Driver");
+MODULE_LICENSE("GPL");