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, 129 insertions, 0 deletions

diff --git a/drivers/zorro/proc.c b/drivers/zorro/proc.c
new file mode 100644
index 000000000..f916bf60b
--- /dev/null
+++ b/drivers/zorro/proc.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	Procfs interface for the Zorro bus.
+ *
+ *	Copyright (C) 1998-2003 Geert Uytterhoeven
+ *
+ *	Heavily based on the procfs interface for the PCI bus, which is
+ *
+ *	Copyright (C) 1997, 1998 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
+ */
+
+#include <linux/types.h>
+#include <linux/zorro.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/export.h>
+
+#include <asm/byteorder.h>
+#include <linux/uaccess.h>
+#include <asm/amigahw.h>
+#include <asm/setup.h>
+
+static loff_t
+proc_bus_zorro_lseek(struct file *file, loff_t off, int whence)
+{
+	return fixed_size_llseek(file, off, whence, sizeof(struct ConfigDev));
+}
+
+static ssize_t
+proc_bus_zorro_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+	struct zorro_dev *z = pde_data(file_inode(file));
+	struct ConfigDev cd;
+	loff_t pos = *ppos;
+
+	if (pos >= sizeof(struct ConfigDev))
+		return 0;
+	if (nbytes >= sizeof(struct ConfigDev))
+		nbytes = sizeof(struct ConfigDev);
+	if (pos + nbytes > sizeof(struct ConfigDev))
+		nbytes = sizeof(struct ConfigDev) - pos;
+
+	/* Construct a ConfigDev */
+	memset(&cd, 0, sizeof(cd));
+	cd.cd_Rom = z->rom;
+	cd.cd_SlotAddr = cpu_to_be16(z->slotaddr);
+	cd.cd_SlotSize = cpu_to_be16(z->slotsize);
+	cd.cd_BoardAddr = cpu_to_be32(zorro_resource_start(z));
+	cd.cd_BoardSize = cpu_to_be32(zorro_resource_len(z));
+
+	if (copy_to_user(buf, (void *)&cd + pos, nbytes))
+		return -EFAULT;
+	*ppos += nbytes;
+
+	return nbytes;
+}
+
+static const struct proc_ops bus_zorro_proc_ops = {
+	.proc_lseek	= proc_bus_zorro_lseek,
+	.proc_read	= proc_bus_zorro_read,
+};
+
+static void * zorro_seq_start(struct seq_file *m, loff_t *pos)
+{
+	return (*pos < zorro_num_autocon) ? pos : NULL;
+}
+
+static void * zorro_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	return (*pos < zorro_num_autocon) ? pos : NULL;
+}
+
+static void zorro_seq_stop(struct seq_file *m, void *v)
+{
+}
+
+static int zorro_seq_show(struct seq_file *m, void *v)
+{
+	unsigned int slot = *(loff_t *)v;
+	struct zorro_dev *z = &zorro_autocon[slot];
+
+	seq_printf(m, "%02x\t%08x\t%08lx\t%08lx\t%02x\n", slot, z->id,
+		   (unsigned long)zorro_resource_start(z),
+		   (unsigned long)zorro_resource_len(z),
+		   z->rom.er_Type);
+	return 0;
+}
+
+static const struct seq_operations zorro_devices_seq_ops = {
+	.start = zorro_seq_start,
+	.next  = zorro_seq_next,
+	.stop  = zorro_seq_stop,
+	.show  = zorro_seq_show,
+};
+
+static struct proc_dir_entry *proc_bus_zorro_dir;
+
+static int __init zorro_proc_attach_device(unsigned int slot)
+{
+	struct proc_dir_entry *entry;
+	char name[4];
+
+	sprintf(name, "%02x", slot);
+	entry = proc_create_data(name, 0, proc_bus_zorro_dir,
+				 &bus_zorro_proc_ops,
+				 &zorro_autocon[slot]);
+	if (!entry)
+		return -ENOMEM;
+	proc_set_size(entry, sizeof(struct zorro_dev));
+	return 0;
+}
+
+static int __init zorro_proc_init(void)
+{
+	unsigned int slot;
+
+	if (MACH_IS_AMIGA && AMIGAHW_PRESENT(ZORRO)) {
+		proc_bus_zorro_dir = proc_mkdir("bus/zorro", NULL);
+		proc_create_seq("devices", 0, proc_bus_zorro_dir,
+			    &zorro_devices_seq_ops);
+		for (slot = 0; slot < zorro_num_autocon; slot++)
+			zorro_proc_attach_device(slot);
+	}
+	return 0;
+}
+
+device_initcall(zorro_proc_init);