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/package/install-extmod-build b/scripts/package/install-extmod-build
new file mode 100755
index 000000000..f12e1ffe4
--- /dev/null
+++ b/scripts/package/install-extmod-build
@@ -0,0 +1,75 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+
+set -eu
+
+destdir=${1}
+
+is_enabled() {
+	grep -q "^$1=y" include/config/auto.conf
+}
+
+find_in_scripts() {
+	find scripts \
+		\( -name atomic -o -name dtc -o -name kconfig -o -name package \) -prune -o \
+		! -name unifdef -a ! -name mk_elfconfig -a \( -type f -o -type l \) -print
+}
+
+mkdir -p "${destdir}"
+
+(
+	cd "${srctree}"
+	echo Makefile
+	find "arch/${SRCARCH}" -maxdepth 1 -name 'Makefile*'
+	find "arch/${SRCARCH}" -name generated -prune -o -name include -type d -print
+	find "arch/${SRCARCH}" -name Kbuild.platforms -o -name Platform
+	find include \( -name config -o -name generated \) -prune -o \( -type f -o -type l \) -print
+	find_in_scripts
+) | tar -c -f - -C "${srctree}" -T - | tar -xf - -C "${destdir}"
+
+{
+	if is_enabled CONFIG_OBJTOOL; then
+		echo tools/objtool/objtool
+	fi
+
+	if is_enabled CONFIG_DEBUG_INFO_BTF_MODULES; then
+		echo tools/bpf/resolve_btfids/resolve_btfids
+	fi
+
+	echo Module.symvers
+	echo "arch/${SRCARCH}/include/generated"
+	echo include/config/auto.conf
+	echo include/config/kernel.release
+	echo include/generated
+	find_in_scripts
+
+	if is_enabled CONFIG_GCC_PLUGINS; then
+		find scripts/gcc-plugins -name '*.so'
+	fi
+} | tar -c -f - -T - | tar -xf - -C "${destdir}"
+
+# When ${CC} and ${HOSTCC} differ, rebuild host programs using ${CC}.
+#
+# This caters to host programs that participate in Kbuild. objtool and
+# resolve_btfids are out of scope.
+if [ "${CC}" != "${HOSTCC}" ]; then
+	cat "${destdir}/scripts/Makefile" - <<-'EOF' > "${destdir}/scripts/Kbuild"
+	subdir-y += basic
+	hostprogs-always-y += mod/modpost
+	mod/modpost-objs := $(addprefix mod/, modpost.o file2alias.o sumversion.o symsearch.o)
+	EOF
+
+	# HOSTCXX is not overridden. The C++ compiler is used to build:
+	# - scripts/kconfig/qconf, which is unneeded for external module builds
+	# - GCC plugins, which will not work on the installed system even after
+	#   being rebuilt.
+	#
+	# Clear VPATH and srcroot because the source files reside in the output
+	# directory.
+	# shellcheck disable=SC2016 # $(MAKE) and $(build) will be expanded by Make
+	"${MAKE}" run-command KBUILD_RUN_COMMAND='+$(MAKE) HOSTCC="'"${CC}"'" VPATH= srcroot=. $(build)='"$(realpath --relative-to=. "${destdir}")"/scripts
+
+	rm -f "${destdir}/scripts/Kbuild"
+fi
+
+find "${destdir}" \( -name '.*.cmd' -o -name '*.o' \) -delete