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, 163 insertions, 0 deletions

diff --git a/drivers/input/input-compat.c b/drivers/input/input-compat.c
new file mode 100644
index 000000000..a5043193e
--- /dev/null
+++ b/drivers/input/input-compat.c
@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 32bit compatibility wrappers for the input subsystem.
+ *
+ * Very heavily based on evdev.c - Copyright (c) 1999-2002 Vojtech Pavlik
+ */
+
+#include <linux/export.h>
+#include <linux/sprintf.h>
+#include <linux/uaccess.h>
+#include "input-compat.h"
+
+#ifdef CONFIG_COMPAT
+
+int input_event_from_user(const char __user *buffer,
+			  struct input_event *event)
+{
+	if (in_compat_syscall() && !COMPAT_USE_64BIT_TIME) {
+		struct input_event_compat compat_event;
+
+		if (copy_from_user(&compat_event, buffer,
+				   sizeof(struct input_event_compat)))
+			return -EFAULT;
+
+		event->input_event_sec = compat_event.sec;
+		event->input_event_usec = compat_event.usec;
+		event->type = compat_event.type;
+		event->code = compat_event.code;
+		event->value = compat_event.value;
+
+	} else {
+		if (copy_from_user(event, buffer, sizeof(struct input_event)))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+int input_event_to_user(char __user *buffer,
+			const struct input_event *event)
+{
+	if (in_compat_syscall() && !COMPAT_USE_64BIT_TIME) {
+		struct input_event_compat compat_event;
+
+		compat_event.sec = event->input_event_sec;
+		compat_event.usec = event->input_event_usec;
+		compat_event.type = event->type;
+		compat_event.code = event->code;
+		compat_event.value = event->value;
+
+		if (copy_to_user(buffer, &compat_event,
+				 sizeof(struct input_event_compat)))
+			return -EFAULT;
+
+	} else {
+		if (copy_to_user(buffer, event, sizeof(struct input_event)))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+int input_ff_effect_from_user(const char __user *buffer, size_t size,
+			      struct ff_effect *effect)
+{
+	if (in_compat_syscall()) {
+		struct ff_effect_compat *compat_effect;
+
+		if (size != sizeof(struct ff_effect_compat))
+			return -EINVAL;
+
+		/*
+		 * It so happens that the pointer which needs to be changed
+		 * is the last field in the structure, so we can retrieve the
+		 * whole thing and replace just the pointer.
+		 */
+		compat_effect = (struct ff_effect_compat *)effect;
+
+		if (copy_from_user(compat_effect, buffer,
+				   sizeof(struct ff_effect_compat)))
+			return -EFAULT;
+
+		if (compat_effect->type == FF_PERIODIC &&
+		    compat_effect->u.periodic.waveform == FF_CUSTOM)
+			effect->u.periodic.custom_data =
+				compat_ptr(compat_effect->u.periodic.custom_data);
+	} else {
+		if (size != sizeof(struct ff_effect))
+			return -EINVAL;
+
+		if (copy_from_user(effect, buffer, sizeof(struct ff_effect)))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+int input_bits_to_string(char *buf, int buf_size, unsigned long bits,
+			 bool skip_empty)
+{
+	int len = 0;
+
+	if (in_compat_syscall()) {
+		u32 dword = bits >> 32;
+		if (dword || !skip_empty)
+			len += snprintf(buf, buf_size, "%x ", dword);
+
+		dword = bits & 0xffffffffUL;
+		if (dword || !skip_empty || len)
+			len += snprintf(buf + len, max(buf_size - len, 0),
+					"%x", dword);
+	} else {
+		if (bits || !skip_empty)
+			len += snprintf(buf, buf_size, "%lx", bits);
+	}
+
+	return len;
+}
+
+#else
+
+int input_event_from_user(const char __user *buffer,
+			 struct input_event *event)
+{
+	if (copy_from_user(event, buffer, sizeof(struct input_event)))
+		return -EFAULT;
+
+	return 0;
+}
+
+int input_event_to_user(char __user *buffer,
+			const struct input_event *event)
+{
+	if (copy_to_user(buffer, event, sizeof(struct input_event)))
+		return -EFAULT;
+
+	return 0;
+}
+
+int input_ff_effect_from_user(const char __user *buffer, size_t size,
+			      struct ff_effect *effect)
+{
+	if (size != sizeof(struct ff_effect))
+		return -EINVAL;
+
+	if (copy_from_user(effect, buffer, sizeof(struct ff_effect)))
+		return -EFAULT;
+
+	return 0;
+}
+
+int input_bits_to_string(char *buf, int buf_size, unsigned long bits,
+			 bool skip_empty)
+{
+	return bits || !skip_empty ?
+		snprintf(buf, buf_size, "%lx", bits) : 0;
+}
+
+#endif /* CONFIG_COMPAT */
+
+EXPORT_SYMBOL_GPL(input_event_from_user);
+EXPORT_SYMBOL_GPL(input_event_to_user);
+EXPORT_SYMBOL_GPL(input_ff_effect_from_user);