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, 119 insertions, 0 deletions

diff --git a/drivers/mfd/menf21bmc.c b/drivers/mfd/menf21bmc.c
new file mode 100644
index 000000000..0f24de516
--- /dev/null
+++ b/drivers/mfd/menf21bmc.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  MEN 14F021P00 Board Management Controller (BMC) MFD Core Driver.
+ *
+ *  Copyright (C) 2014 MEN Mikro Elektronik Nuernberg GmbH
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+
+#define BMC_CMD_WDT_EXIT_PROD	0x18
+#define BMC_CMD_WDT_PROD_STAT	0x19
+#define BMC_CMD_REV_MAJOR	0x80
+#define BMC_CMD_REV_MINOR	0x81
+#define BMC_CMD_REV_MAIN	0x82
+
+static struct mfd_cell menf21bmc_cell[] = {
+	{ .name = "menf21bmc_wdt", },
+	{ .name = "menf21bmc_led", },
+	{ .name = "menf21bmc_hwmon", }
+};
+
+static int menf21bmc_wdt_exit_prod_mode(struct i2c_client *client)
+{
+	int val, ret;
+
+	val = i2c_smbus_read_byte_data(client, BMC_CMD_WDT_PROD_STAT);
+	if (val < 0)
+		return val;
+
+	/*
+	 * Production mode should be not active after delivery of the Board.
+	 * To be sure we check it, inform the user and exit the mode
+	 * if active.
+	 */
+	if (val == 0x00) {
+		dev_info(&client->dev,
+			"BMC in production mode. Exit production mode\n");
+
+		ret = i2c_smbus_write_byte(client, BMC_CMD_WDT_EXIT_PROD);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int
+menf21bmc_probe(struct i2c_client *client)
+{
+	int rev_major, rev_minor, rev_main;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA |
+						      I2C_FUNC_SMBUS_WORD_DATA |
+						      I2C_FUNC_SMBUS_BYTE))
+		return -ENODEV;
+
+	rev_major = i2c_smbus_read_word_data(client, BMC_CMD_REV_MAJOR);
+	if (rev_major < 0) {
+		dev_err(&client->dev, "failed to get BMC major revision\n");
+		return rev_major;
+	}
+
+	rev_minor = i2c_smbus_read_word_data(client, BMC_CMD_REV_MINOR);
+	if (rev_minor < 0) {
+		dev_err(&client->dev, "failed to get BMC minor revision\n");
+		return rev_minor;
+	}
+
+	rev_main = i2c_smbus_read_word_data(client, BMC_CMD_REV_MAIN);
+	if (rev_main < 0) {
+		dev_err(&client->dev, "failed to get BMC main revision\n");
+		return rev_main;
+	}
+
+	dev_info(&client->dev, "FW Revision: %02d.%02d.%02d\n",
+		 rev_major, rev_minor, rev_main);
+
+	/*
+	 * We have to exit the Production Mode of the BMC to activate the
+	 * Watchdog functionality and the BIOS life sign monitoring.
+	 */
+	ret = menf21bmc_wdt_exit_prod_mode(client);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed to leave production mode\n");
+		return ret;
+	}
+
+	ret = devm_mfd_add_devices(&client->dev, 0, menf21bmc_cell,
+				   ARRAY_SIZE(menf21bmc_cell), NULL, 0, NULL);
+	if (ret < 0) {
+		dev_err(&client->dev, "failed to add BMC sub-devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id menf21bmc_id_table[] = {
+	{ "menf21bmc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, menf21bmc_id_table);
+
+static struct i2c_driver menf21bmc_driver = {
+	.driver.name	= "menf21bmc",
+	.id_table	= menf21bmc_id_table,
+	.probe		= menf21bmc_probe,
+};
+
+module_i2c_driver(menf21bmc_driver);
+
+MODULE_DESCRIPTION("MEN 14F021P00 BMC mfd core driver");
+MODULE_AUTHOR("Andreas Werner <andreas.werner@men.de>");
+MODULE_LICENSE("GPL v2");