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, 133 insertions, 0 deletions

diff --git a/drivers/reset/reset-zynq.c b/drivers/reset/reset-zynq.c
new file mode 100644
index 000000000..688b51288
--- /dev/null
+++ b/drivers/reset/reset-zynq.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2015, National Instruments Corp.
+ *
+ * Xilinx Zynq Reset controller driver
+ *
+ * Author: Moritz Fischer <moritz.fischer@ettus.com>
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+struct zynq_reset_data {
+	struct regmap *slcr;
+	struct reset_controller_dev rcdev;
+	u32 offset;
+};
+
+#define to_zynq_reset_data(p)		\
+	container_of((p), struct zynq_reset_data, rcdev)
+
+static int zynq_reset_assert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	return regmap_update_bits(priv->slcr,
+				  priv->offset + (bank * 4),
+				  BIT(offset),
+				  BIT(offset));
+}
+
+static int zynq_reset_deassert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	return regmap_update_bits(priv->slcr,
+				  priv->offset + (bank * 4),
+				  BIT(offset),
+				  ~BIT(offset));
+}
+
+static int zynq_reset_status(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	struct zynq_reset_data *priv = to_zynq_reset_data(rcdev);
+
+	int bank = id / BITS_PER_LONG;
+	int offset = id % BITS_PER_LONG;
+	int ret;
+	u32 reg;
+
+	pr_debug("%s: %s reset bank %u offset %u\n", KBUILD_MODNAME, __func__,
+		 bank, offset);
+
+	ret = regmap_read(priv->slcr, priv->offset + (bank * 4), &reg);
+	if (ret)
+		return ret;
+
+	return !!(reg & BIT(offset));
+}
+
+static const struct reset_control_ops zynq_reset_ops = {
+	.assert		= zynq_reset_assert,
+	.deassert	= zynq_reset_deassert,
+	.status		= zynq_reset_status,
+};
+
+static int zynq_reset_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct zynq_reset_data *priv;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->slcr = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
+						     "syscon");
+	if (IS_ERR(priv->slcr)) {
+		dev_err(&pdev->dev, "unable to get zynq-slcr regmap");
+		return PTR_ERR(priv->slcr);
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "missing IO resource\n");
+		return -ENODEV;
+	}
+
+	priv->offset = res->start;
+
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = resource_size(res) / 4 * BITS_PER_LONG;
+	priv->rcdev.ops = &zynq_reset_ops;
+	priv->rcdev.of_node = pdev->dev.of_node;
+
+	return devm_reset_controller_register(&pdev->dev, &priv->rcdev);
+}
+
+static const struct of_device_id zynq_reset_dt_ids[] = {
+	{ .compatible = "xlnx,zynq-reset", },
+	{ /* sentinel */ },
+};
+
+static struct platform_driver zynq_reset_driver = {
+	.probe	= zynq_reset_probe,
+	.driver = {
+		.name		= KBUILD_MODNAME,
+		.of_match_table	= zynq_reset_dt_ids,
+	},
+};
+builtin_platform_driver(zynq_reset_driver);