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, 66 insertions, 0 deletions

diff --git a/include/uapi/asm-generic/termbits-common.h b/include/uapi/asm-generic/termbits-common.h
new file mode 100644
index 000000000..4a6a79f28
--- /dev/null
+++ b/include/uapi/asm-generic/termbits-common.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __ASM_GENERIC_TERMBITS_COMMON_H
+#define __ASM_GENERIC_TERMBITS_COMMON_H
+
+typedef unsigned char	cc_t;
+typedef unsigned int	speed_t;
+
+/* c_iflag bits */
+#define IGNBRK	0x001			/* Ignore break condition */
+#define BRKINT	0x002			/* Signal interrupt on break */
+#define IGNPAR	0x004			/* Ignore characters with parity errors */
+#define PARMRK	0x008			/* Mark parity and framing errors */
+#define INPCK	0x010			/* Enable input parity check */
+#define ISTRIP	0x020			/* Strip 8th bit off characters */
+#define INLCR	0x040			/* Map NL to CR on input */
+#define IGNCR	0x080			/* Ignore CR */
+#define ICRNL	0x100			/* Map CR to NL on input */
+#define IXANY	0x800			/* Any character will restart after stop */
+
+/* c_oflag bits */
+#define OPOST	0x01			/* Perform output processing */
+#define OCRNL	0x08
+#define ONOCR	0x10
+#define ONLRET	0x20
+#define OFILL	0x40
+#define OFDEL	0x80
+
+/* c_cflag bit meaning */
+/* Common CBAUD rates */
+#define     B0		0x00000000	/* hang up */
+#define    B50		0x00000001
+#define    B75		0x00000002
+#define   B110		0x00000003
+#define   B134		0x00000004
+#define   B150		0x00000005
+#define   B200		0x00000006
+#define   B300		0x00000007
+#define   B600		0x00000008
+#define  B1200		0x00000009
+#define  B1800		0x0000000a
+#define  B2400		0x0000000b
+#define  B4800		0x0000000c
+#define  B9600		0x0000000d
+#define B19200		0x0000000e
+#define B38400		0x0000000f
+#define EXTA		B19200
+#define EXTB		B38400
+
+#define ADDRB		0x20000000	/* address bit */
+#define CMSPAR		0x40000000	/* mark or space (stick) parity */
+#define CRTSCTS		0x80000000	/* flow control */
+
+#define IBSHIFT		16		/* Shift from CBAUD to CIBAUD */
+
+/* tcflow() ACTION argument and TCXONC use these */
+#define TCOOFF		0		/* Suspend output */
+#define TCOON		1		/* Restart suspended output */
+#define TCIOFF		2		/* Send a STOP character */
+#define TCION		3		/* Send a START character */
+
+/* tcflush() QUEUE_SELECTOR argument and TCFLSH use these */
+#define TCIFLUSH	0		/* Discard data received but not yet read */
+#define TCOFLUSH	1		/* Discard data written but not yet sent */
+#define TCIOFLUSH	2		/* Discard all pending data */
+
+#endif /* __ASM_GENERIC_TERMBITS_COMMON_H */