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, 290 insertions, 0 deletions

diff --git a/scripts/atomic/atomic-tbl.sh b/scripts/atomic/atomic-tbl.sh
new file mode 100755
index 000000000..608ff39eb
--- /dev/null
+++ b/scripts/atomic/atomic-tbl.sh
@@ -0,0 +1,290 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# helpers for dealing with atomics.tbl
+
+#meta_in(meta, match)
+meta_in()
+{
+	case "$1" in
+	[$2]) return 0;;
+	esac
+
+	return 1
+}
+
+#meta_has_ret(meta)
+meta_has_ret()
+{
+	meta_in "$1" "bBiIfFlR"
+}
+
+#meta_has_acquire(meta)
+meta_has_acquire()
+{
+	meta_in "$1" "BFIlR"
+}
+
+#meta_has_release(meta)
+meta_has_release()
+{
+	meta_in "$1" "BFIRs"
+}
+
+#meta_has_relaxed(meta)
+meta_has_relaxed()
+{
+	meta_in "$1" "BFIR"
+}
+
+#meta_is_implicitly_relaxed(meta)
+meta_is_implicitly_relaxed()
+{
+	meta_in "$1" "vls"
+}
+
+#find_template(tmpltype, pfx, name, sfx, order)
+find_template()
+{
+	local tmpltype="$1"; shift
+	local pfx="$1"; shift
+	local name="$1"; shift
+	local sfx="$1"; shift
+	local order="$1"; shift
+
+	local base=""
+	local file=""
+
+	# We may have fallbacks for a specific case (e.g. read_acquire()), or
+	# an entire class, e.g. *inc*().
+	#
+	# Start at the most specific, and fall back to the most general. Once
+	# we find a specific fallback, don't bother looking for more.
+	for base in "${pfx}${name}${sfx}${order}" "${pfx}${name}${sfx}" "${name}"; do
+		file="${ATOMICDIR}/${tmpltype}/${base}"
+
+		if [ -f "${file}" ]; then
+			printf "${file}"
+			break
+		fi
+	done
+}
+
+#find_fallback_template(pfx, name, sfx, order)
+find_fallback_template()
+{
+	find_template "fallbacks" "$@"
+}
+
+#find_kerneldoc_template(pfx, name, sfx, order)
+find_kerneldoc_template()
+{
+	find_template "kerneldoc" "$@"
+}
+
+#gen_ret_type(meta, int)
+gen_ret_type() {
+	local meta="$1"; shift
+	local int="$1"; shift
+
+	case "${meta}" in
+	[sv]) printf "void";;
+	[bB]) printf "bool";;
+	[aiIfFlR]) printf "${int}";;
+	esac
+}
+
+#gen_ret_stmt(meta)
+gen_ret_stmt()
+{
+	if meta_has_ret "${meta}"; then
+		printf "return ";
+	fi
+}
+
+# gen_param_name(arg)
+gen_param_name()
+{
+	# strip off the leading 'c' for 'cv'
+	local name="${1#c}"
+	printf "${name#*:}"
+}
+
+# gen_param_type(arg, int, atomic)
+gen_param_type()
+{
+	local type="${1%%:*}"; shift
+	local int="$1"; shift
+	local atomic="$1"; shift
+
+	case "${type}" in
+	i) type="${int} ";;
+	p) type="${int} *";;
+	v) type="${atomic}_t *";;
+	cv) type="const ${atomic}_t *";;
+	esac
+
+	printf "${type}"
+}
+
+#gen_param(arg, int, atomic)
+gen_param()
+{
+	local arg="$1"; shift
+	local int="$1"; shift
+	local atomic="$1"; shift
+	local name="$(gen_param_name "${arg}")"
+	local type="$(gen_param_type "${arg}" "${int}" "${atomic}")"
+
+	printf "${type}${name}"
+}
+
+#gen_params(int, atomic, arg...)
+gen_params()
+{
+	local int="$1"; shift
+	local atomic="$1"; shift
+
+	while [ "$#" -gt 0 ]; do
+		gen_param "$1" "${int}" "${atomic}"
+		[ "$#" -gt 1 ] && printf ", "
+		shift;
+	done
+}
+
+#gen_args(arg...)
+gen_args()
+{
+	while [ "$#" -gt 0 ]; do
+		printf "$(gen_param_name "$1")"
+		[ "$#" -gt 1 ] && printf ", "
+		shift;
+	done
+}
+
+#gen_desc_return(meta)
+gen_desc_return()
+{
+	local meta="$1"; shift
+
+	case "${meta}" in
+	[v])
+		printf "Return: Nothing."
+		;;
+	[Ff])
+		printf "Return: The original value of @v."
+		;;
+	[R])
+		printf "Return: The updated value of @v."
+		;;
+	[l])
+		printf "Return: The value of @v."
+		;;
+	esac
+}
+
+#gen_template_kerneldoc(template, class, meta, pfx, name, sfx, order, atomic, int, args...)
+gen_template_kerneldoc()
+{
+	local template="$1"; shift
+	local class="$1"; shift
+	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}" "${int}")"
+	local retstmt="$(gen_ret_stmt "${meta}")"
+	local params="$(gen_params "${int}" "${atomic}" "$@")"
+	local args="$(gen_args "$@")"
+	local desc_order=""
+	local desc_instrumentation=""
+	local desc_return=""
+
+	if [ ! -z "${order}" ]; then
+		desc_order="${order##_}"
+	elif meta_is_implicitly_relaxed "${meta}"; then
+		desc_order="relaxed"
+	else
+		desc_order="full"
+	fi
+
+	if [ -z "${class}" ]; then
+		desc_noinstr="Unsafe to use in noinstr code; use raw_${atomicname}() there."
+	else
+		desc_noinstr="Safe to use in noinstr code; prefer ${atomicname}() elsewhere."
+	fi
+
+	desc_return="$(gen_desc_return "${meta}")"
+
+	. ${template}
+}
+
+#gen_kerneldoc(class, meta, pfx, name, sfx, order, atomic, int, args...)
+gen_kerneldoc()
+{
+	local class="$1"; shift
+	local meta="$1"; shift
+	local pfx="$1"; shift
+	local name="$1"; shift
+	local sfx="$1"; shift
+	local order="$1"; shift
+
+	local atomicname="${atomic}_${pfx}${name}${sfx}${order}"
+
+	local tmpl="$(find_kerneldoc_template "${pfx}" "${name}" "${sfx}" "${order}")"
+	if [ -z "${tmpl}" ]; then
+		printf "/*\n"
+		printf " * No kerneldoc available for ${class}${atomicname}\n"
+		printf " */\n"
+	else
+	gen_template_kerneldoc "${tmpl}" "${class}" "${meta}" "${pfx}" "${name}" "${sfx}" "${order}" "$@"
+	fi
+}
+
+#gen_proto_order_variants(meta, pfx, name, sfx, ...)
+gen_proto_order_variants()
+{
+	local meta="$1"; shift
+	local pfx="$1"; shift
+	local name="$1"; shift
+	local sfx="$1"; shift
+
+	gen_proto_order_variant "${meta}" "${pfx}" "${name}" "${sfx}" "" "$@"
+
+	if meta_has_acquire "${meta}"; then
+		gen_proto_order_variant "${meta}" "${pfx}" "${name}" "${sfx}" "_acquire" "$@"
+	fi
+	if meta_has_release "${meta}"; then
+		gen_proto_order_variant "${meta}" "${pfx}" "${name}" "${sfx}" "_release" "$@"
+	fi
+	if meta_has_relaxed "${meta}"; then
+		gen_proto_order_variant "${meta}" "${pfx}" "${name}" "${sfx}" "_relaxed" "$@"
+	fi
+}
+
+#gen_proto_variants(meta, name, ...)
+gen_proto_variants()
+{
+	local meta="$1"; shift
+	local name="$1"; shift
+	local pfx=""
+	local sfx=""
+
+	meta_in "${meta}" "fF" && pfx="fetch_"
+	meta_in "${meta}" "R" && sfx="_return"
+
+	gen_proto_order_variants "${meta}" "${pfx}" "${name}" "${sfx}" "$@"
+}
+
+#gen_proto(meta, ...)
+gen_proto() {
+	local meta="$1"; shift
+	for m in $(echo "${meta}" | grep -o .); do
+		gen_proto_variants "${m}" "$@"
+	done
+}