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, 126 insertions, 0 deletions

diff --git a/drivers/char/nsc_gpio.c b/drivers/char/nsc_gpio.c
new file mode 100644
index 000000000..2c9b12b85
--- /dev/null
+++ b/drivers/char/nsc_gpio.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* linux/drivers/char/nsc_gpio.c
+
+   National Semiconductor common GPIO device-file/VFS methods.
+   Allows a user space process to control the GPIO pins.
+
+   Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
+   Copyright (c) 2005      Jim Cromie <jim.cromie@gmail.com>
+*/
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/nsc_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/uaccess.h>
+#include <asm/io.h>
+
+#define NAME "nsc_gpio"
+
+void nsc_gpio_dump(struct nsc_gpio_ops *amp, unsigned index)
+{
+	/* retrieve current config w/o changing it */
+	u32 config = amp->gpio_config(index, ~0, 0);
+
+	/* user requested via 'v' command, so its INFO */
+	dev_info(amp->dev, "io%02u: 0x%04x %s %s %s %s %s %s %s\tio:%d/%d\n",
+		 index, config,
+		 (config & 1) ? "OE" : "TS",      /* output-enabled/tristate */
+		 (config & 2) ? "PP" : "OD",      /* push pull / open drain */
+		 (config & 4) ? "PUE" : "PUD",    /* pull up enabled/disabled */
+		 (config & 8) ? "LOCKED" : "",    /* locked / unlocked */
+		 (config & 16) ? "LEVEL" : "EDGE",/* level/edge input */
+		 (config & 32) ? "HI" : "LO",     /* trigger on rise/fall edge */
+		 (config & 64) ? "DEBOUNCE" : "", /* debounce */
+
+		 amp->gpio_get(index), amp->gpio_current(index));
+}
+
+ssize_t nsc_gpio_write(struct file *file, const char __user *data,
+		       size_t len, loff_t *ppos)
+{
+	unsigned m = iminor(file_inode(file));
+	struct nsc_gpio_ops *amp = file->private_data;
+	struct device *dev = amp->dev;
+	size_t i;
+	int err = 0;
+
+	for (i = 0; i < len; ++i) {
+		char c;
+		if (get_user(c, data + i))
+			return -EFAULT;
+		switch (c) {
+		case '0':
+			amp->gpio_set(m, 0);
+			break;
+		case '1':
+			amp->gpio_set(m, 1);
+			break;
+		case 'O':
+			dev_dbg(dev, "GPIO%d output enabled\n", m);
+			amp->gpio_config(m, ~1, 1);
+			break;
+		case 'o':
+			dev_dbg(dev, "GPIO%d output disabled\n", m);
+			amp->gpio_config(m, ~1, 0);
+			break;
+		case 'T':
+			dev_dbg(dev, "GPIO%d output is push pull\n", m);
+			amp->gpio_config(m, ~2, 2);
+			break;
+		case 't':
+			dev_dbg(dev, "GPIO%d output is open drain\n", m);
+			amp->gpio_config(m, ~2, 0);
+			break;
+		case 'P':
+			dev_dbg(dev, "GPIO%d pull up enabled\n", m);
+			amp->gpio_config(m, ~4, 4);
+			break;
+		case 'p':
+			dev_dbg(dev, "GPIO%d pull up disabled\n", m);
+			amp->gpio_config(m, ~4, 0);
+			break;
+		case 'v':
+			/* View Current pin settings */
+			amp->gpio_dump(amp, m);
+			break;
+		case '\n':
+			/* end of settings string, do nothing */
+			break;
+		default:
+			dev_err(dev, "io%2d bad setting: chr<0x%2x>\n",
+				m, (int)c);
+			err++;
+		}
+	}
+	if (err)
+		return -EINVAL;	/* full string handled, report error */
+
+	return len;
+}
+
+ssize_t nsc_gpio_read(struct file *file, char __user * buf,
+		      size_t len, loff_t * ppos)
+{
+	unsigned m = iminor(file_inode(file));
+	int value;
+	struct nsc_gpio_ops *amp = file->private_data;
+
+	value = amp->gpio_get(m);
+	if (put_user(value ? '1' : '0', buf))
+		return -EFAULT;
+
+	return 1;
+}
+
+/* common file-ops routines for both scx200_gpio and pc87360_gpio */
+EXPORT_SYMBOL(nsc_gpio_write);
+EXPORT_SYMBOL(nsc_gpio_read);
+EXPORT_SYMBOL(nsc_gpio_dump);
+
+MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
+MODULE_DESCRIPTION("NatSemi GPIO Common Methods");
+MODULE_LICENSE("GPL");