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, 113 insertions, 0 deletions

diff --git a/drivers/reset/reset-eic7700-hsp.c b/drivers/reset/reset-eic7700-hsp.c
new file mode 100644
index 000000000..1575ee4a2
--- /dev/null
+++ b/drivers/reset/reset-eic7700-hsp.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2026, Beijing ESWIN Computing Technology Co., Ltd..
+ * All rights reserved.
+ *
+ * ESWIN EIC7700 HSP Reset Driver
+ *
+ * Authors: Xuyang Dong <dongxuyang@eswincomputing.com>
+ */
+
+#include <linux/auxiliary_bus.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+
+#include <dt-bindings/reset/eswin,eic7700-hspcrg.h>
+
+/**
+ * struct eic7700_hsp_reset_data - reset controller information structure
+ * @rcdev: reset controller entity
+ * @regmap: regmap handle containing the memory-mapped reset registers
+ */
+struct eic7700_hsp_reset_data {
+	struct reset_controller_dev rcdev;
+	struct regmap *regmap;
+};
+
+struct eic7700_hsp_reg {
+	u32 reg;
+	u32 bit;
+	bool active_low;
+};
+
+static inline struct eic7700_hsp_reset_data *
+to_eic7700_hsp_reset(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct eic7700_hsp_reset_data, rcdev);
+}
+
+static const struct eic7700_hsp_reg eic7700_hsp_reset[] = {
+	[EIC7700_HSP_RST_SATA_P0]	= {0x340, BIT(0), false},
+	[EIC7700_HSP_RST_SATA_PHY]	= {0x340, BIT(1), false},
+	[EIC7700_HSP_RST_USB0]		= {0x800, BIT(24), true},
+	[EIC7700_HSP_RST_USB1]		= {0x900, BIT(24), true},
+	[EIC7700_HSP_RST_USB0_PHY]	= {0x800, BIT(25), false},
+	[EIC7700_HSP_RST_USB1_PHY]	= {0x900, BIT(25), false},
+};
+
+static int eic7700_hsp_reset_assert(struct reset_controller_dev *rcdev,
+				    unsigned long id)
+{
+	struct eic7700_hsp_reset_data *data = to_eic7700_hsp_reset(rcdev);
+
+	return regmap_assign_bits(data->regmap, eic7700_hsp_reset[id].reg,
+				  eic7700_hsp_reset[id].bit,
+				  !eic7700_hsp_reset[id].active_low);
+}
+
+static int eic7700_hsp_reset_deassert(struct reset_controller_dev *rcdev,
+				      unsigned long id)
+{
+	struct eic7700_hsp_reset_data *data = to_eic7700_hsp_reset(rcdev);
+
+	return regmap_assign_bits(data->regmap, eic7700_hsp_reset[id].reg,
+				  eic7700_hsp_reset[id].bit,
+				  eic7700_hsp_reset[id].active_low);
+}
+
+static const struct reset_control_ops eic7700_hsp_reset_ops = {
+	.assert = eic7700_hsp_reset_assert,
+	.deassert = eic7700_hsp_reset_deassert,
+};
+
+static int eic7700_hsp_reset_probe(struct auxiliary_device *adev,
+				   const struct auxiliary_device_id *id)
+{
+	struct eic7700_hsp_reset_data *data;
+	struct device *dev = &adev->dev;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->regmap = dev_get_regmap(dev->parent, NULL);
+	if (!data->regmap)
+		return dev_err_probe(dev, -ENODEV, "failed to get regmap!\n");
+
+	data->rcdev.owner = THIS_MODULE;
+	data->rcdev.ops = &eic7700_hsp_reset_ops;
+	data->rcdev.of_node = dev->parent->of_node;
+	data->rcdev.dev = dev;
+	data->rcdev.nr_resets = ARRAY_SIZE(eic7700_hsp_reset);
+
+	return devm_reset_controller_register(dev, &data->rcdev);
+}
+
+static const struct auxiliary_device_id eic7700_hsp_reset_ids[] = {
+	{ .name = "clk_eic7700_hsp.hsp-reset", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(auxiliary, eic7700_hsp_reset_ids);
+
+static struct auxiliary_driver eic7700_hsp_reset_driver = {
+	.probe	= eic7700_hsp_reset_probe,
+	.id_table = eic7700_hsp_reset_ids,
+};
+
+module_auxiliary_driver(eic7700_hsp_reset_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Xuyang Dong <dongxuyang@eswincomputing.com>");
+MODULE_DESCRIPTION("ESWIN EIC7700 HSP Reset Controller Driver");