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, 75 insertions, 0 deletions

diff --git a/scripts/headers_install.sh b/scripts/headers_install.sh
new file mode 100755
index 000000000..2f1d1767c
--- /dev/null
+++ b/scripts/headers_install.sh
@@ -0,0 +1,75 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+if [ $# -ne 2 ]
+then
+	echo "Usage: headers_install.sh INFILE OUTFILE"
+	echo
+	echo "Prepares kernel header files for use by user space, by removing"
+	echo "all compiler.h definitions and #includes, removing any"
+	echo "#ifdef __KERNEL__ sections, and putting __underscores__ around"
+	echo "asm/inline/volatile keywords."
+	echo
+	echo "INFILE: header file to operate on"
+	echo "OUTFILE: output file which the processed header is written to"
+
+	exit 1
+fi
+
+# Grab arguments
+INFILE=$1
+OUTFILE=$2
+TMPFILE=$OUTFILE.tmp
+
+trap 'rm -f $OUTFILE $TMPFILE' EXIT
+
+# SPDX-License-Identifier with GPL variants must have "WITH Linux-syscall-note"
+if [ -n "$(sed -n -e "/SPDX-License-Identifier:.*GPL-/{/WITH Linux-syscall-note/!p}" $INFILE)" ]; then
+	echo "error: $INFILE: missing \"WITH Linux-syscall-note\" for SPDX-License-Identifier" >&2
+	exit 1
+fi
+
+sed -E -e '
+	s/([[:space:](])(__user|__force|__iomem)[[:space:]]/\1/g
+	s/__attribute_const__([[:space:]]|$)/\1/g
+	s@^#include <linux/compiler.h>@@
+	s/(^|[^a-zA-Z0-9])__packed([^a-zA-Z0-9_]|$)/\1__attribute__((packed))\2/g
+	s/(^|[[:space:](])(inline|asm|volatile)([[:space:](]|$)/\1__\2__\3/g
+	s@#(ifndef|define|endif[[:space:]]*/[*])[[:space:]]*_UAPI@#\1 @
+	s/__ASSEMBLY__/__ASSEMBLER__/g
+' $INFILE > $TMPFILE || exit 1
+
+scripts/unifdef -U__KERNEL__ -D__EXPORTED_HEADERS__ $TMPFILE > $OUTFILE
+[ $? -gt 1 ] && exit 1
+
+# Remove /* ... */ style comments, and find CONFIG_ references in code
+configs=$(sed -e '
+:comment
+	s:/\*[^*][^*]*:/*:
+	s:/\*\*\**\([^/]\):/*\1:
+	t comment
+	s:/\*\*/: :
+	t comment
+	/\/\*/! b check
+	N
+	b comment
+:print
+	P
+	D
+:check
+	s:^\(CONFIG_[[:alnum:]_]*\):\1\n:
+	t print
+	s:^[[:alnum:]_][[:alnum:]_]*::
+	s:^[^[:alnum:]_][^[:alnum:]_]*::
+	t check
+	d
+' $OUTFILE)
+
+for c in $configs
+do
+	echo "error: $INFILE: leak $c to user-space" >&2
+	exit 1
+done
+
+rm -f $TMPFILE
+trap - EXIT