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, 97 insertions, 0 deletions

diff --git a/scripts/package/mkspec b/scripts/package/mkspec
new file mode 100755
index 000000000..c604f8c17
--- /dev/null
+++ b/scripts/package/mkspec
@@ -0,0 +1,97 @@
+#!/bin/sh
+#
+#	Output a simple RPM spec file.
+#	This version assumes a minimum of RPM 4.13
+#
+#	The only gothic bit here is redefining install_post to avoid
+#	stripping the symbols from files in the kernel which we want
+#
+#	Patched for non-x86 by Opencon (L) 2002 <opencon@rio.skydome.net>
+#
+
+set -eu
+
+output=$1
+
+mkdir -p "$(dirname "${output}")"
+
+exec >"${output}"
+
+if grep -q CONFIG_MODULES=y include/config/auto.conf; then
+echo '%define with_devel %{?_without_devel: 0} %{?!_without_devel: 1}'
+else
+echo '%define with_devel 0'
+fi
+
+# use %{debug_package} machinery to generate -debuginfo
+with_debuginfo_rpm=0
+# manually generate -debuginfo package
+with_debuginfo_manual=0
+# debuginfo package generation uses find-debuginfo.sh under the hood,
+# which only works on uncompressed modules that contain debuginfo
+if grep -q CONFIG_DEBUG_INFO=y include/config/auto.conf &&
+   (! grep -q CONFIG_MODULE_COMPRESS=y include/config/auto.conf) &&
+   (! grep -q CONFIG_DEBUG_INFO_SPLIT=y include/config/auto.conf); then
+	# If module signing is enabled (which may be required to boot with
+	# lockdown enabled), the find-debuginfo.sh machinery cannot be used
+	# because the signatures will be stripped off the modules. However, due
+	# to an rpm bug in versions prior to 4.20.0
+	#
+	#     https://github.com/rpm-software-management/rpm/issues/3057
+	#     https://github.com/rpm-software-management/rpm/commit/49f906998f3cf1f4152162ca61ac0869251c380f
+	#
+	# We cannot provide our own debuginfo package because it does not listen
+	# to our custom files list, failing the build due to unpackaged files.
+	# Manually generate the debug info package if using rpm 4.20.0. If not
+	# using rpm 4.20.0, avoid generating a -debuginfo package altogether,
+	# as it is not safe.
+	if grep -q CONFIG_MODULE_SIG=y include/config/auto.conf; then
+		rpm_ver_str=$(rpm --version 2>/dev/null)
+		# Split the version on spaces
+		IFS=' '
+		set -- $rpm_ver_str
+		if [ "${1:-}" = RPM -a "${2:-}" = version ]; then
+			IFS=.
+			set -- $3
+			rpm_ver=$(( 1000000 * $1 + 10000 * $2 + 100 * $3 + ${4:-0} ))
+			if [ "$rpm_ver" -ge 4200000 ]; then
+				with_debuginfo_manual='%{?_without_debuginfo:0}%{?!_without_debuginfo:1}'
+			fi
+		fi
+	else
+		with_debuginfo_rpm='%{?_without_debuginfo:0}%{?!_without_debuginfo:1}'
+	fi
+fi
+echo "%define with_debuginfo_manual $with_debuginfo_manual"
+echo "%define with_debuginfo_rpm $with_debuginfo_rpm"
+
+cat<<EOF
+%define ARCH ${ARCH}
+%define KERNELRELEASE ${KERNELRELEASE}
+%define pkg_release $("${srctree}/scripts/build-version")
+EOF
+
+cat "${srctree}/scripts/package/kernel.spec"
+
+# collect the user's name and email address for the changelog entry
+if [ "$(command -v git)" ]; then
+	name=$(git config user.name) || true
+	email=$(git config user.email) || true
+fi
+
+if [ ! "${name:+set}" ]; then
+	name=${KBUILD_BUILD_USER:-$(id -nu)}
+fi
+
+if [ ! "${email:+set}" ]; then
+	buildhost=${KBUILD_BUILD_HOST:-$(hostname -f 2>/dev/null || hostname)}
+	builduser=${KBUILD_BUILD_USER:-$(id -nu)}
+	email="${builduser}@${buildhost}"
+fi
+
+cat << EOF
+
+%changelog
+* $(LC_ALL=C date +'%a %b %d %Y') ${name} <${email}>
+- Custom built Linux kernel.
+EOF