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, 203 insertions, 0 deletions

diff --git a/drivers/mfd/altera-sysmgr.c b/drivers/mfd/altera-sysmgr.c
new file mode 100644
index 000000000..90c6902d5
--- /dev/null
+++ b/drivers/mfd/altera-sysmgr.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Copyright (C) 2018-2019, Intel Corporation.
+ *  Copyright (C) 2012 Freescale Semiconductor, Inc.
+ *  Copyright (C) 2012 Linaro Ltd.
+ *
+ *  Based on syscon driver.
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mfd/altera-sysmgr.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+/**
+ * struct altr_sysmgr - Altera SOCFPGA System Manager
+ * @regmap: the regmap used for System Manager accesses.
+ */
+struct altr_sysmgr {
+	struct regmap   *regmap;
+};
+
+static struct platform_driver altr_sysmgr_driver;
+
+/**
+ * s10_protected_reg_write
+ * Write to a protected SMC register.
+ * @base: Base address of System Manager
+ * @reg:  Address offset of register
+ * @val:  Value to write
+ * Return: INTEL_SIP_SMC_STATUS_OK (0) on success
+ *	   INTEL_SIP_SMC_REG_ERROR on error
+ *	   INTEL_SIP_SMC_RETURN_UNKNOWN_FUNCTION if not supported
+ */
+static int s10_protected_reg_write(void *base,
+				   unsigned int reg, unsigned int val)
+{
+	struct arm_smccc_res result;
+	unsigned long sysmgr_base = (unsigned long)base;
+
+	arm_smccc_smc(INTEL_SIP_SMC_REG_WRITE, sysmgr_base + reg,
+		      val, 0, 0, 0, 0, 0, &result);
+
+	return (int)result.a0;
+}
+
+/**
+ * s10_protected_reg_read
+ * Read the status of a protected SMC register
+ * @base: Base address of System Manager.
+ * @reg:  Address of register
+ * @val:  Value read.
+ * Return: INTEL_SIP_SMC_STATUS_OK (0) on success
+ *	   INTEL_SIP_SMC_REG_ERROR on error
+ *	   INTEL_SIP_SMC_RETURN_UNKNOWN_FUNCTION if not supported
+ */
+static int s10_protected_reg_read(void *base,
+				  unsigned int reg, unsigned int *val)
+{
+	struct arm_smccc_res result;
+	unsigned long sysmgr_base = (unsigned long)base;
+
+	arm_smccc_smc(INTEL_SIP_SMC_REG_READ, sysmgr_base + reg,
+		      0, 0, 0, 0, 0, 0, &result);
+
+	*val = (unsigned int)result.a1;
+
+	return (int)result.a0;
+}
+
+static struct regmap_config altr_sysmgr_regmap_cfg = {
+	.name = "altr_sysmgr",
+	.reg_bits = 32,
+	.reg_stride = 4,
+	.val_bits = 32,
+	.fast_io = true,
+	.use_single_read = true,
+	.use_single_write = true,
+};
+
+/**
+ * altr_sysmgr_regmap_lookup_by_phandle
+ * Find the sysmgr previous configured in probe() and return regmap property.
+ * Return: regmap if found or error if not found.
+ *
+ * @np: Pointer to device's Device Tree node
+ * @property: Device Tree property name which references the sysmgr
+ */
+struct regmap *altr_sysmgr_regmap_lookup_by_phandle(struct device_node *np,
+						    const char *property)
+{
+	struct device *dev;
+	struct altr_sysmgr *sysmgr;
+	struct device_node *sysmgr_np;
+
+	if (property)
+		sysmgr_np = of_parse_phandle(np, property, 0);
+	else
+		sysmgr_np = np;
+
+	if (!sysmgr_np)
+		return ERR_PTR(-ENODEV);
+
+	dev = driver_find_device_by_of_node(&altr_sysmgr_driver.driver,
+					    (void *)sysmgr_np);
+	if (property)
+		of_node_put(sysmgr_np);
+
+	if (!dev)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	sysmgr = dev_get_drvdata(dev);
+
+	put_device(dev);
+
+	return sysmgr->regmap;
+}
+EXPORT_SYMBOL_GPL(altr_sysmgr_regmap_lookup_by_phandle);
+
+static int sysmgr_probe(struct platform_device *pdev)
+{
+	struct altr_sysmgr *sysmgr;
+	struct regmap *regmap;
+	struct resource *res;
+	struct regmap_config sysmgr_config = altr_sysmgr_regmap_cfg;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	void __iomem *base;
+
+	sysmgr = devm_kzalloc(dev, sizeof(*sysmgr), GFP_KERNEL);
+	if (!sysmgr)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENOENT;
+
+	sysmgr_config.max_register = resource_size(res) -
+				     sysmgr_config.reg_stride;
+	if (of_device_is_compatible(np, "altr,sys-mgr-s10")) {
+		sysmgr_config.reg_read = s10_protected_reg_read;
+		sysmgr_config.reg_write = s10_protected_reg_write;
+
+		/* Need physical address for SMCC call */
+		regmap = devm_regmap_init(dev, NULL,
+					  (void *)(uintptr_t)res->start,
+					  &sysmgr_config);
+	} else {
+		base = devm_ioremap(dev, res->start, resource_size(res));
+		if (!base)
+			return -ENOMEM;
+
+		sysmgr_config.max_register = resource_size(res) - 4;
+		regmap = devm_regmap_init_mmio(dev, base, &sysmgr_config);
+	}
+
+	if (IS_ERR(regmap)) {
+		pr_err("regmap init failed\n");
+		return PTR_ERR(regmap);
+	}
+
+	sysmgr->regmap = regmap;
+
+	platform_set_drvdata(pdev, sysmgr);
+
+	return 0;
+}
+
+static const struct of_device_id altr_sysmgr_of_match[] = {
+	{ .compatible = "altr,sys-mgr" },
+	{ .compatible = "altr,sys-mgr-s10" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, altr_sysmgr_of_match);
+
+static struct platform_driver altr_sysmgr_driver = {
+	.probe =  sysmgr_probe,
+	.driver = {
+		.name = "altr,system_manager",
+		.of_match_table = altr_sysmgr_of_match,
+	},
+};
+
+static int __init altr_sysmgr_init(void)
+{
+	return platform_driver_register(&altr_sysmgr_driver);
+}
+core_initcall(altr_sysmgr_init);
+
+static void __exit altr_sysmgr_exit(void)
+{
+	platform_driver_unregister(&altr_sysmgr_driver);
+}
+module_exit(altr_sysmgr_exit);
+
+MODULE_AUTHOR("Thor Thayer <>");
+MODULE_DESCRIPTION("SOCFPGA System Manager driver");