From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration 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 Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- tools/testing/selftests/cpu-hotplug/Makefile | 11 + .../selftests/cpu-hotplug/cpu-on-off-test.sh | 225 +++++++++++++++++++++ 2 files changed, 236 insertions(+) create mode 100644 tools/testing/selftests/cpu-hotplug/Makefile create mode 100755 tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh (limited to 'tools/testing/selftests/cpu-hotplug') diff --git a/tools/testing/selftests/cpu-hotplug/Makefile b/tools/testing/selftests/cpu-hotplug/Makefile new file mode 100644 index 000000000..8b66c4738 --- /dev/null +++ b/tools/testing/selftests/cpu-hotplug/Makefile @@ -0,0 +1,11 @@ +# SPDX-License-Identifier: GPL-2.0 +all: + +TEST_PROGS := cpu-on-off-test.sh + +include ../lib.mk + +run_full_test: + @/bin/bash ./cpu-on-off-test.sh -a && echo "cpu-hotplug selftests: [PASS]" || echo "cpu-hotplug selftests: [FAIL]" + +clean: diff --git a/tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh b/tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh new file mode 100755 index 000000000..287cfd580 --- /dev/null +++ b/tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh @@ -0,0 +1,225 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 + +SYSFS= +# Kselftest framework requirement - SKIP code is 4. +ksft_skip=4 +retval=0 + +prerequisite() +{ + msg="skip all tests:" + + if [ $UID != 0 ]; then + echo $msg must be run as root >&2 + exit $ksft_skip + fi + + taskset -p 01 $$ + + SYSFS=`mount -t sysfs | head -1 | awk '{ print $3 }'` + + if [ ! -d "$SYSFS" ]; then + echo $msg sysfs is not mounted >&2 + exit $ksft_skip + fi + + if ! ls $SYSFS/devices/system/cpu/cpu*/online > /dev/null 2>&1; then + echo $msg cpu hotplug is not supported >&2 + exit $ksft_skip + fi + + echo "CPU online/offline summary:" + online_cpus=`cat $SYSFS/devices/system/cpu/online` + online_max=${online_cpus##*-} + + if [[ "$online_cpus" = "$online_max" ]]; then + echo "$msg: since there is only one cpu: $online_cpus" + exit $ksft_skip + fi + + present_cpus=`cat $SYSFS/devices/system/cpu/present` + present_max=${present_cpus##*-} + echo "present_cpus = $present_cpus present_max = $present_max" + + echo -e "\t Cpus in online state: $online_cpus" + + offline_cpus=`cat $SYSFS/devices/system/cpu/offline` + if [[ "a$offline_cpus" = "a" ]]; then + offline_cpus=0 + else + offline_max=${offline_cpus##*-} + fi + echo -e "\t Cpus in offline state: $offline_cpus" +} + +# +# list all hot-pluggable CPUs +# +hotpluggable_cpus() +{ + local state=${1:-.\*} + + for cpu in $SYSFS/devices/system/cpu/cpu*; do + if [ -f $cpu/online ] && grep -q $state $cpu/online; then + echo ${cpu##/*/cpu} + fi + done +} + +hotpluggable_offline_cpus() +{ + hotpluggable_cpus 0 +} + +hotpluggable_online_cpus() +{ + hotpluggable_cpus 1 +} + +cpu_is_online() +{ + grep -q 1 $SYSFS/devices/system/cpu/cpu$1/online +} + +cpu_is_offline() +{ + grep -q 0 $SYSFS/devices/system/cpu/cpu$1/online +} + +online_cpu() +{ + echo 1 > $SYSFS/devices/system/cpu/cpu$1/online +} + +offline_cpu() +{ + echo 0 > $SYSFS/devices/system/cpu/cpu$1/online +} + +online_cpu_expect_success() +{ + local cpu=$1 + + if ! online_cpu $cpu; then + echo $FUNCNAME $cpu: unexpected fail >&2 + retval=1 + elif ! cpu_is_online $cpu; then + echo $FUNCNAME $cpu: unexpected offline >&2 + retval=1 + fi +} + +online_cpu_expect_fail() +{ + local cpu=$1 + + if online_cpu $cpu 2> /dev/null; then + echo $FUNCNAME $cpu: unexpected success >&2 + retval=1 + elif ! cpu_is_offline $cpu; then + echo $FUNCNAME $cpu: unexpected online >&2 + retval=1 + fi +} + +offline_cpu_expect_success() +{ + local cpu=$1 + + if ! offline_cpu $cpu; then + echo $FUNCNAME $cpu: unexpected fail >&2 + retval=1 + elif ! cpu_is_offline $cpu; then + echo $FUNCNAME $cpu: unexpected offline >&2 + retval=1 + fi +} + +offline_cpu_expect_fail() +{ + local cpu=$1 + + if offline_cpu $cpu 2> /dev/null; then + echo $FUNCNAME $cpu: unexpected success >&2 + retval=1 + elif ! cpu_is_online $cpu; then + echo $FUNCNAME $cpu: unexpected offline >&2 + retval=1 + fi +} + +online_all_hot_pluggable_cpus() +{ + for cpu in `hotpluggable_offline_cpus`; do + online_cpu_expect_success $cpu + done +} + +offline_all_hot_pluggable_cpus() +{ + local reserve_cpu=$online_max + for cpu in `hotpluggable_online_cpus`; do + # Reserve one cpu oneline at least. + if [ $cpu -eq $reserve_cpu ];then + continue + fi + offline_cpu_expect_success $cpu + done +} + +allcpus=0 +online_cpus=0 +online_max=0 +offline_cpus=0 +offline_max=0 +present_cpus=0 +present_max=0 + +while getopts ah opt; do + case $opt in + a) + allcpus=1 + ;; + h) + echo "Usage $0 [ -a ]" + echo -e "\t default offline one cpu" + echo -e "\t run with -a option to offline all cpus" + exit + ;; + esac +done + +prerequisite + +# +# Safe test (default) - offline and online one cpu +# +if [ $allcpus -eq 0 ]; then + echo "Limited scope test: one hotplug cpu" + echo -e "\t (leaves cpu in the original state):" + echo -e "\t online to offline to online: cpu $online_max" + offline_cpu_expect_success $online_max + online_cpu_expect_success $online_max + + if [[ $offline_cpus -gt 0 ]]; then + echo -e "\t online to offline to online: cpu $present_max" + online_cpu_expect_success $present_max + offline_cpu_expect_success $present_max + online_cpu $present_max + fi + exit $retval +else + echo "Full scope test: all hotplug cpus" + echo -e "\t online all offline cpus" + echo -e "\t offline all online cpus" + echo -e "\t online all offline cpus" +fi + +online_all_hot_pluggable_cpus + +offline_all_hot_pluggable_cpus + +online_all_hot_pluggable_cpus + +exit $retval -- cgit v1.3.1