KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.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
+}