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/kho/arm64.conf | 9 ++ tools/testing/selftests/kho/init.c | 75 +++++++++++++ tools/testing/selftests/kho/vmtest.sh | 190 +++++++++++++++++++++++++++++++++ tools/testing/selftests/kho/x86.conf | 7 ++ 4 files changed, 281 insertions(+) create mode 100644 tools/testing/selftests/kho/arm64.conf create mode 100644 tools/testing/selftests/kho/init.c create mode 100755 tools/testing/selftests/kho/vmtest.sh create mode 100644 tools/testing/selftests/kho/x86.conf (limited to 'tools/testing/selftests/kho') diff --git a/tools/testing/selftests/kho/arm64.conf b/tools/testing/selftests/kho/arm64.conf new file mode 100644 index 000000000..ee696807c --- /dev/null +++ b/tools/testing/selftests/kho/arm64.conf @@ -0,0 +1,9 @@ +QEMU_CMD="qemu-system-aarch64 -M virt -cpu max" +QEMU_KCONFIG=" +CONFIG_SERIAL_AMBA_PL010=y +CONFIG_SERIAL_AMBA_PL010_CONSOLE=y +CONFIG_SERIAL_AMBA_PL011=y +CONFIG_SERIAL_AMBA_PL011_CONSOLE=y +" +KERNEL_IMAGE="Image" +KERNEL_CMDLINE="console=ttyAMA0" diff --git a/tools/testing/selftests/kho/init.c b/tools/testing/selftests/kho/init.c new file mode 100644 index 000000000..88a41b6eb --- /dev/null +++ b/tools/testing/selftests/kho/init.c @@ -0,0 +1,75 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include +#include +#include +#include + +/* from arch/x86/include/asm/setup.h */ +#define COMMAND_LINE_SIZE 2048 + +#define KERNEL_IMAGE "/kernel" + +static int mount_filesystems(void) +{ + if (mount("debugfs", "/debugfs", "debugfs", 0, NULL) < 0) + return -1; + + return mount("proc", "/proc", "proc", 0, NULL); +} + +static long kexec_file_load(int kernel_fd, int initrd_fd, + unsigned long cmdline_len, const char *cmdline, + unsigned long flags) +{ + return syscall(__NR_kexec_file_load, kernel_fd, initrd_fd, cmdline_len, + cmdline, flags); +} + +static int kexec_load(void) +{ + char cmdline[COMMAND_LINE_SIZE]; + ssize_t len; + int fd, err; + + fd = open("/proc/cmdline", O_RDONLY); + if (fd < 0) + return -1; + + len = read(fd, cmdline, sizeof(cmdline)); + close(fd); + if (len < 0) + return -1; + + /* replace \n with \0 */ + cmdline[len - 1] = 0; + fd = open(KERNEL_IMAGE, O_RDONLY); + if (fd < 0) + return -1; + + err = kexec_file_load(fd, -1, len, cmdline, KEXEC_FILE_NO_INITRAMFS); + close(fd); + + return err ? : 0; +} + +int main(int argc, char *argv[]) +{ + if (mount_filesystems()) + goto err_reboot; + + if (kexec_load()) + goto err_reboot; + + if (reboot(RB_KEXEC)) + goto err_reboot; + + return 0; + +err_reboot: + reboot(RB_AUTOBOOT); + return -1; +} diff --git a/tools/testing/selftests/kho/vmtest.sh b/tools/testing/selftests/kho/vmtest.sh new file mode 100755 index 000000000..0014bd76e --- /dev/null +++ b/tools/testing/selftests/kho/vmtest.sh @@ -0,0 +1,190 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 + +set -ue + +CROSS_COMPILE="${CROSS_COMPILE:-""}" + +test_dir=$(realpath "$(dirname "$0")") +kernel_dir=$(realpath "$test_dir/../../../..") + +tmp_dir=$(mktemp -d /tmp/kho-test.XXXXXXXX) +headers_dir="$tmp_dir/usr" +initrd="$tmp_dir/initrd.cpio" + +source "$test_dir/../kselftest/ktap_helpers.sh" + +function usage() { + cat < "$kho_config" </dev/null || skip "$opt is missing" + done < "$kho_config" + + $make_cmd "$kimage" + $make_cmd headers_install INSTALL_HDR_PATH="$headers_dir" +} + +function mkinitrd() { + local kernel=$1 + + "$CROSS_COMPILE"gcc -s -static -Os -nostdinc -nostdlib \ + -fno-asynchronous-unwind-tables -fno-ident \ + -I "$headers_dir/include" \ + -I "$kernel_dir/tools/include/nolibc" \ + -o "$tmp_dir/init" "$test_dir/init.c" + + cat > "$tmp_dir/cpio_list" < "$initrd" +} + +function run_qemu() { + local qemu_cmd=$1 + local cmdline=$2 + local kernel=$3 + local serial="$tmp_dir/qemu.serial" + + cmdline="$cmdline kho=on panic=-1" + + $qemu_cmd -m 1G -smp 2 -no-reboot -nographic -nodefaults \ + -accel kvm -accel hvf -accel tcg \ + -serial file:"$serial" \ + -append "$cmdline" \ + -kernel "$kernel" \ + -initrd "$initrd" + + grep "KHO restore succeeded" "$serial" &> /dev/null || fail "KHO failed" +} + +function target_to_arch() { + local target=$1 + + case $target in + aarch64) echo "arm64" ;; + x86_64) echo "x86" ;; + *) skip "architecture $target is not supported" + esac +} + +function main() { + local build_dir="$kernel_dir/.kho" + local jobs=$(($(nproc) * 2)) + local target="$(uname -m)" + + # skip the test if any of the preparation steps fails + set -o errtrace + trap skip ERR + + while getopts 'hd:j:t:' opt; do + case $opt in + d) + build_dir="$OPTARG" + ;; + j) + jobs="$OPTARG" + ;; + t) + target="$OPTARG" + ;; + h) + usage + exit 0 + ;; + *) + echo Unknown argument "$opt" + usage + exit 1 + ;; + esac + done + + ktap_print_header + ktap_set_plan 1 + + if [[ "$target" != "$(uname -m)" ]] && [[ -z "$CROSS_COMPILE" ]]; then + skip "Cross-platform testing needs to specify CROSS_COMPILE" + fi + + mkdir -p "$build_dir" + local arch=$(target_to_arch "$target") + source "$test_dir/$arch.conf" + + # build the kernel and create initrd + # initrd includes the kernel image that will be kexec'ed + local make_cmd="make ARCH=$arch CROSS_COMPILE=$CROSS_COMPILE -j$jobs" + build_kernel "$build_dir" "$make_cmd" "$QEMU_KCONFIG" "$KERNEL_IMAGE" + + local kernel="$build_dir/arch/$arch/boot/$KERNEL_IMAGE" + mkinitrd "$kernel" + + run_qemu "$QEMU_CMD" "$KERNEL_CMDLINE" "$kernel" + + ktap_test_pass "KHO succeeded" +} + +main "$@" diff --git a/tools/testing/selftests/kho/x86.conf b/tools/testing/selftests/kho/x86.conf new file mode 100644 index 000000000..b419e610c --- /dev/null +++ b/tools/testing/selftests/kho/x86.conf @@ -0,0 +1,7 @@ +QEMU_CMD=qemu-system-x86_64 +QEMU_KCONFIG=" +CONFIG_SERIAL_8250=y +CONFIG_SERIAL_8250_CONSOLE=y +" +KERNEL_IMAGE="bzImage" +KERNEL_CMDLINE="console=ttyS0" -- cgit v1.3.1