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>

3 files changed, 150 insertions, 0 deletions

diff --git a/drivers/soc/litex/Kconfig b/drivers/soc/litex/Kconfig
new file mode 100644
index 000000000..f3f869639
--- /dev/null
+++ b/drivers/soc/litex/Kconfig
@@ -0,0 +1,20 @@
+# SPDX-License_Identifier: GPL-2.0
+
+menu "Enable LiteX SoC Builder specific drivers"
+
+config LITEX
+	bool
+
+config LITEX_SOC_CONTROLLER
+	tristate "Enable LiteX SoC Controller driver"
+	depends on OF
+	depends on HAS_IOMEM
+	select LITEX
+	help
+	  This option enables the SoC Controller Driver which verifies
+	  LiteX CSR access and provides common litex_[read|write]*
+	  accessors.
+	  All drivers that use functions from litex.h must depend on
+	  LITEX.
+
+endmenu
diff --git a/drivers/soc/litex/Makefile b/drivers/soc/litex/Makefile
new file mode 100644
index 000000000..98ff7325b
--- /dev/null
+++ b/drivers/soc/litex/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License_Identifier: GPL-2.0
+
+obj-$(CONFIG_LITEX_SOC_CONTROLLER)	+= litex_soc_ctrl.o
diff --git a/drivers/soc/litex/litex_soc_ctrl.c b/drivers/soc/litex/litex_soc_ctrl.c
new file mode 100644
index 000000000..104a5f9bf
--- /dev/null
+++ b/drivers/soc/litex/litex_soc_ctrl.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LiteX SoC Controller Driver
+ *
+ * Copyright (C) 2020 Antmicro <www.antmicro.com>
+ *
+ */
+
+#include <linux/litex.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/reboot.h>
+
+/* reset register located at the base address */
+#define RESET_REG_OFF           0x00
+#define RESET_REG_VALUE         0x00000001
+
+#define SCRATCH_REG_OFF         0x04
+#define SCRATCH_REG_VALUE       0x12345678
+#define SCRATCH_TEST_VALUE      0xdeadbeef
+
+/*
+ * Check LiteX CSR read/write access
+ *
+ * This function reads and writes a scratch register in order to verify if CSR
+ * access works.
+ *
+ * In case any problems are detected, the driver should panic.
+ *
+ * Access to the LiteX CSR is, by design, done in CPU native endianness.
+ * The driver should not dynamically configure access functions when
+ * the endianness mismatch is detected. Such situation indicates problems in
+ * the soft SoC design and should be solved at the LiteX generator level,
+ * not in the software.
+ */
+static int litex_check_csr_access(void __iomem *reg_addr)
+{
+	unsigned long reg;
+
+	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
+
+	if (reg != SCRATCH_REG_VALUE) {
+		panic("Scratch register read error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
+			SCRATCH_REG_VALUE, reg);
+		return -EINVAL;
+	}
+
+	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_TEST_VALUE);
+	reg = litex_read32(reg_addr + SCRATCH_REG_OFF);
+
+	if (reg != SCRATCH_TEST_VALUE) {
+		panic("Scratch register write error - the system is probably broken! Expected: 0x%x but got: 0x%lx",
+			SCRATCH_TEST_VALUE, reg);
+		return -EINVAL;
+	}
+
+	/* restore original value of the SCRATCH register */
+	litex_write32(reg_addr + SCRATCH_REG_OFF, SCRATCH_REG_VALUE);
+
+	pr_info("LiteX SoC Controller driver initialized");
+
+	return 0;
+}
+
+struct litex_soc_ctrl_device {
+	void __iomem *base;
+};
+
+static int litex_reset_handler(struct sys_off_data *data)
+{
+	struct litex_soc_ctrl_device *soc_ctrl_dev = data->cb_data;
+
+	litex_write32(soc_ctrl_dev->base + RESET_REG_OFF, RESET_REG_VALUE);
+	return NOTIFY_DONE;
+}
+
+static const struct of_device_id litex_soc_ctrl_of_match[] = {
+	{.compatible = "litex,soc-controller"},
+	{},
+};
+MODULE_DEVICE_TABLE(of, litex_soc_ctrl_of_match);
+
+static int litex_soc_ctrl_probe(struct platform_device *pdev)
+{
+	struct litex_soc_ctrl_device *soc_ctrl_dev;
+	int error;
+
+	soc_ctrl_dev = devm_kzalloc(&pdev->dev, sizeof(*soc_ctrl_dev), GFP_KERNEL);
+	if (!soc_ctrl_dev)
+		return -ENOMEM;
+
+	soc_ctrl_dev->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(soc_ctrl_dev->base))
+		return PTR_ERR(soc_ctrl_dev->base);
+
+	error = litex_check_csr_access(soc_ctrl_dev->base);
+	if (error)
+		return error;
+
+	error = devm_register_restart_handler(&pdev->dev,
+					      litex_reset_handler,
+					      soc_ctrl_dev);
+	if (error) {
+		dev_warn(&pdev->dev, "cannot register restart handler: %d\n",
+			 error);
+	}
+
+	return 0;
+}
+
+static struct platform_driver litex_soc_ctrl_driver = {
+	.driver = {
+		.name = "litex-soc-controller",
+		.of_match_table = litex_soc_ctrl_of_match,
+	},
+	.probe = litex_soc_ctrl_probe,
+};
+
+module_platform_driver(litex_soc_ctrl_driver);
+MODULE_DESCRIPTION("LiteX SoC Controller driver");
+MODULE_AUTHOR("Antmicro <www.antmicro.com>");
+MODULE_LICENSE("GPL v2");