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, 205 insertions, 0 deletions

diff --git a/drivers/macintosh/ans-lcd.c b/drivers/macintosh/ans-lcd.c
new file mode 100644
index 000000000..fa904b24a
--- /dev/null
+++ b/drivers/macintosh/ans-lcd.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * /dev/lcd driver for Apple Network Servers.
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/fcntl.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/fs.h>
+#include <linux/of.h>
+
+#include <linux/uaccess.h>
+#include <asm/sections.h>
+#include <asm/io.h>
+
+#include "ans-lcd.h"
+
+#define ANSLCD_ADDR		0xf301c000
+#define ANSLCD_CTRL_IX 0x00
+#define ANSLCD_DATA_IX 0x10
+
+static unsigned long anslcd_short_delay = 80;
+static unsigned long anslcd_long_delay = 3280;
+static volatile unsigned char __iomem *anslcd_ptr;
+static DEFINE_MUTEX(anslcd_mutex);
+
+#undef DEBUG
+
+static void
+anslcd_write_byte_ctrl ( unsigned char c )
+{
+#ifdef DEBUG
+	printk(KERN_DEBUG "LCD: CTRL byte: %02x\n",c);
+#endif
+	out_8(anslcd_ptr + ANSLCD_CTRL_IX, c);
+	switch(c) {
+		case 1:
+		case 2:
+		case 3:
+			udelay(anslcd_long_delay); break;
+		default: udelay(anslcd_short_delay);
+	}
+}
+
+static void
+anslcd_write_byte_data ( unsigned char c )
+{
+	out_8(anslcd_ptr + ANSLCD_DATA_IX, c);
+	udelay(anslcd_short_delay);
+}
+
+static ssize_t
+anslcd_write( struct file * file, const char __user * buf, 
+				size_t count, loff_t *ppos )
+{
+	const char __user *p = buf;
+	int i;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "LCD: write\n");
+#endif
+
+	if (!access_ok(buf, count))
+		return -EFAULT;
+
+	mutex_lock(&anslcd_mutex);
+	for ( i = *ppos; count > 0; ++i, ++p, --count ) 
+	{
+		char c;
+		__get_user(c, p);
+		anslcd_write_byte_data( c );
+	}
+	mutex_unlock(&anslcd_mutex);
+	*ppos = i;
+	return p - buf;
+}
+
+static long
+anslcd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	char ch, __user *temp;
+	long ret = 0;
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "LCD: ioctl(%d,%d)\n",cmd,arg);
+#endif
+
+	mutex_lock(&anslcd_mutex);
+
+	switch ( cmd )
+	{
+	case ANSLCD_CLEAR:
+		anslcd_write_byte_ctrl ( 0x38 );
+		anslcd_write_byte_ctrl ( 0x0f );
+		anslcd_write_byte_ctrl ( 0x06 );
+		anslcd_write_byte_ctrl ( 0x01 );
+		anslcd_write_byte_ctrl ( 0x02 );
+		break;
+	case ANSLCD_SENDCTRL:
+		temp = (char __user *) arg;
+		__get_user(ch, temp);
+		for (; ch; temp++) { /* FIXME: This is ugly, but should work, as a \0 byte is not a valid command code */
+			anslcd_write_byte_ctrl ( ch );
+			__get_user(ch, temp);
+		}
+		break;
+	case ANSLCD_SETSHORTDELAY:
+		if (!capable(CAP_SYS_ADMIN))
+			ret =-EACCES;
+		else
+			anslcd_short_delay=arg;
+		break;
+	case ANSLCD_SETLONGDELAY:
+		if (!capable(CAP_SYS_ADMIN))
+			ret = -EACCES;
+		else
+			anslcd_long_delay=arg;
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	mutex_unlock(&anslcd_mutex);
+	return ret;
+}
+
+static int
+anslcd_open( struct inode * inode, struct file * file )
+{
+	return 0;
+}
+
+const struct file_operations anslcd_fops = {
+	.write		= anslcd_write,
+	.unlocked_ioctl	= anslcd_ioctl,
+	.open		= anslcd_open,
+	.llseek		= default_llseek,
+};
+
+static struct miscdevice anslcd_dev = {
+	LCD_MINOR,
+	"anslcd",
+	&anslcd_fops
+};
+
+static const char anslcd_logo[] __initconst =
+				"********************"  /* Line #1 */
+				"*      LINUX!      *"  /* Line #3 */
+				"*    Welcome to    *"  /* Line #2 */
+				"********************"; /* Line #4 */
+
+static int __init
+anslcd_init(void)
+{
+	int a;
+	int retval;
+	struct device_node* node;
+
+	node = of_find_node_by_name(NULL, "lcd");
+	if (!node || !of_node_name_eq(node->parent, "gc")) {
+		of_node_put(node);
+		return -ENODEV;
+	}
+	of_node_put(node);
+
+	anslcd_ptr = ioremap(ANSLCD_ADDR, 0x20);
+	
+	retval = misc_register(&anslcd_dev);
+	if(retval < 0){
+		printk(KERN_INFO "LCD: misc_register failed\n");
+		iounmap(anslcd_ptr);
+		return retval;
+	}
+
+#ifdef DEBUG
+	printk(KERN_DEBUG "LCD: init\n");
+#endif
+
+	mutex_lock(&anslcd_mutex);
+	anslcd_write_byte_ctrl ( 0x38 );
+	anslcd_write_byte_ctrl ( 0x0c );
+	anslcd_write_byte_ctrl ( 0x06 );
+	anslcd_write_byte_ctrl ( 0x01 );
+	anslcd_write_byte_ctrl ( 0x02 );
+	for(a=0;a<80;a++) {
+		anslcd_write_byte_data(anslcd_logo[a]);
+	}
+	mutex_unlock(&anslcd_mutex);
+	return 0;
+}
+
+static void __exit
+anslcd_exit(void)
+{
+	misc_deregister(&anslcd_dev);
+	iounmap(anslcd_ptr);
+}
+
+module_init(anslcd_init);
+module_exit(anslcd_exit);
+MODULE_LICENSE("GPL v2");