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, 184 insertions, 0 deletions

diff --git a/scripts/atomic/gen-atomic-instrumented.sh b/scripts/atomic/gen-atomic-instrumented.sh
new file mode 100755
index 000000000..9c1d53f81
--- /dev/null
+++ b/scripts/atomic/gen-atomic-instrumented.sh
@@ -0,0 +1,184 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+ATOMICDIR=$(dirname $0)
+
+. ${ATOMICDIR}/atomic-tbl.sh
+
+#gen_param_check(meta, arg)
+gen_param_check()
+{
+	local meta="$1"; shift
+	local arg="$1"; shift
+	local type="${arg%%:*}"
+	local name="$(gen_param_name "${arg}")"
+	local rw="atomic_write"
+
+	case "${type#c}" in
+	i) return;;
+	esac
+
+	if [ ${type#c} != ${type} ]; then
+		# We don't write to constant parameters.
+		rw="atomic_read"
+	elif [ "${type}" = "p" ] ; then
+		# The "old" argument in try_cmpxchg() gets accessed non-atomically
+		rw="read_write"
+	elif [ "${meta}" != "s" ]; then
+		# An atomic RMW: if this parameter is not a constant, and this atomic is
+		# not just a 's'tore, this parameter is both read from and written to.
+		rw="atomic_read_write"
+	fi
+
+	printf "\tinstrument_${rw}(${name}, sizeof(*${name}));\n"
+}
+
+#gen_params_checks(meta, arg...)
+gen_params_checks()
+{
+	local meta="$1"; shift
+	local order="$1"; shift
+
+	if [ "${order}" = "_release" ]; then
+		printf "\tkcsan_release();\n"
+	elif [ -z "${order}" ] && ! meta_in "$meta" "slv"; then
+		# RMW with return value is fully ordered
+		printf "\tkcsan_mb();\n"
+	fi
+
+	while [ "$#" -gt 0 ]; do
+		gen_param_check "$meta" "$1"
+		shift;
+	done
+}
+
+#gen_proto_order_variant(meta, pfx, name, sfx, order, atomic, int, arg...)
+gen_proto_order_variant()
+{
+	local meta="$1"; shift
+	local pfx="$1"; shift
+	local name="$1"; shift
+	local sfx="$1"; shift
+	local order="$1"; shift
+	local atomic="$1"; shift
+	local int="$1"; shift
+
+	local atomicname="${atomic}_${pfx}${name}${sfx}${order}"
+
+	local ret="$(gen_ret_type "${meta}" "${int}")"
+	local params="$(gen_params "${int}" "${atomic}" "$@")"
+	local checks="$(gen_params_checks "${meta}" "${order}" "$@")"
+	local args="$(gen_args "$@")"
+	local retstmt="$(gen_ret_stmt "${meta}")"
+
+	gen_kerneldoc "" "${meta}" "${pfx}" "${name}" "${sfx}" "${order}" "${atomic}" "${int}" "$@"
+
+cat <<EOF
+static __always_inline ${ret}
+${atomicname}(${params})
+{
+${checks}
+	${retstmt}raw_${atomicname}(${args});
+}
+EOF
+
+	printf "\n"
+}
+
+gen_xchg()
+{
+	local xchg="$1"; shift
+	local order="$1"; shift
+
+	kcsan_barrier=""
+	if [ "${xchg%_local}" = "${xchg}" ]; then
+		case "$order" in
+		_release)	kcsan_barrier="kcsan_release()" ;;
+		"")			kcsan_barrier="kcsan_mb()" ;;
+		esac
+	fi
+
+	if [ "${xchg%${xchg#try_cmpxchg}}" = "try_cmpxchg" ] ; then
+
+cat <<EOF
+#define ${xchg}${order}(ptr, oldp, ...) \\
+({ \\
+	typeof(ptr) __ai_ptr = (ptr); \\
+	typeof(oldp) __ai_oldp = (oldp); \\
+EOF
+[ -n "$kcsan_barrier" ] && printf "\t${kcsan_barrier}; \\\\\n"
+cat <<EOF
+	instrument_atomic_read_write(__ai_ptr, sizeof(*__ai_ptr)); \\
+	instrument_read_write(__ai_oldp, sizeof(*__ai_oldp)); \\
+	raw_${xchg}${order}(__ai_ptr, __ai_oldp, __VA_ARGS__); \\
+})
+EOF
+
+	else
+
+cat <<EOF
+#define ${xchg}${order}(ptr, ...) \\
+({ \\
+	typeof(ptr) __ai_ptr = (ptr); \\
+EOF
+[ -n "$kcsan_barrier" ] && printf "\t${kcsan_barrier}; \\\\\n"
+cat <<EOF
+	instrument_atomic_read_write(__ai_ptr, sizeof(*__ai_ptr)); \\
+	raw_${xchg}${order}(__ai_ptr, __VA_ARGS__); \\
+})
+EOF
+
+	fi
+}
+
+cat << EOF
+// SPDX-License-Identifier: GPL-2.0
+
+// Generated by $0
+// DO NOT MODIFY THIS FILE DIRECTLY
+
+/*
+ * This file provoides atomic operations with explicit instrumentation (e.g.
+ * KASAN, KCSAN), which should be used unless it is necessary to avoid
+ * instrumentation. Where it is necessary to aovid instrumenation, the
+ * raw_atomic*() operations should be used.
+ */
+#ifndef _LINUX_ATOMIC_INSTRUMENTED_H
+#define _LINUX_ATOMIC_INSTRUMENTED_H
+
+#include <linux/build_bug.h>
+#include <linux/compiler.h>
+#include <linux/instrumented.h>
+
+EOF
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic" "int" ${args}
+done
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic64" "s64" ${args}
+done
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic_long" "long" ${args}
+done
+
+
+for xchg in "xchg" "cmpxchg" "cmpxchg64" "cmpxchg128" "try_cmpxchg" "try_cmpxchg64" "try_cmpxchg128"; do
+	for order in "" "_acquire" "_release" "_relaxed"; do
+		gen_xchg "${xchg}" "${order}"
+		printf "\n"
+	done
+done
+
+for xchg in "cmpxchg_local" "cmpxchg64_local" "cmpxchg128_local" "sync_cmpxchg" \
+	    "try_cmpxchg_local" "try_cmpxchg64_local" "try_cmpxchg128_local" "sync_try_cmpxchg"; do
+	gen_xchg "${xchg}" ""
+	printf "\n"
+done
+
+cat <<EOF
+
+#endif /* _LINUX_ATOMIC_INSTRUMENTED_H */
+EOF