tpm_emulator: Have swtpm relock storage upon migration fall-back

Swtpm may release the lock once the last one of its state blobs has been
migrated out. In case of VM migration failure QEMU now needs to notify
swtpm that it should again take the lock, which it can otherwise only do
once it has received the first TPM command from the VM.

Only try to send the lock command if swtpm supports it. It will not have
released the lock (and support shared storage setups) if it doesn't
support the locking command since the functionality of releasing the lock
upon state blob reception and the lock command were added to swtpm
'together'.

If QEMU sends the lock command and the storage has already been locked
no error is reported.

If swtpm does not receive the lock command (from older version of QEMU),
it will lock the storage once the first TPM command has been received. So
sending the lock command is an optimization.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20220912174741.1542330-3-stefanb@linux.ibm.com

2 files changed, 61 insertions, 1 deletions

diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
index 9b50c5b3e2..49cc3d749d 100644
--- a/backends/tpm/tpm_emulator.c
+++ b/backends/tpm/tpm_emulator.c
@@ -35,6 +35,7 @@
 #include "sysemu/runstate.h"
 #include "sysemu/tpm_backend.h"
 #include "sysemu/tpm_util.h"
+#include "sysemu/runstate.h"
 #include "tpm_int.h"
 #include "tpm_ioctl.h"
 #include "migration/blocker.h"
@@ -82,6 +83,9 @@ struct TPMEmulator {
     unsigned int established_flag_cached:1;
 
     TPMBlobBuffers state_blobs;
+
+    bool relock_storage;
+    VMChangeStateEntry *vmstate;
 };
 
 struct tpm_error {
@@ -303,6 +307,35 @@ static int tpm_emulator_stop_tpm(TPMBackend *tb)
     return 0;
 }
 
+static int tpm_emulator_lock_storage(TPMEmulator *tpm_emu)
+{
+    ptm_lockstorage pls;
+
+    if (!TPM_EMULATOR_IMPLEMENTS_ALL_CAPS(tpm_emu, PTM_CAP_LOCK_STORAGE)) {
+        trace_tpm_emulator_lock_storage_cmd_not_supt();
+        return 0;
+    }
+
+    /* give failing side 300 * 10ms time to release lock */
+    pls.u.req.retries = cpu_to_be32(300);
+    if (tpm_emulator_ctrlcmd(tpm_emu, CMD_LOCK_STORAGE, &pls,
+                             sizeof(pls.u.req), sizeof(pls.u.resp)) < 0) {
+        error_report("tpm-emulator: Could not lock storage within 3 seconds: "
+                     "%s", strerror(errno));
+        return -1;
+    }
+
+    pls.u.resp.tpm_result = be32_to_cpu(pls.u.resp.tpm_result);
+    if (pls.u.resp.tpm_result != 0) {
+        error_report("tpm-emulator: TPM result for CMD_LOCK_STORAGE: 0x%x %s",
+                     pls.u.resp.tpm_result,
+                     tpm_emulator_strerror(pls.u.resp.tpm_result));
+        return -1;
+    }
+
+    return 0;
+}
+
 static int tpm_emulator_set_buffer_size(TPMBackend *tb,
                                         size_t wanted_size,
                                         size_t *actual_size)
@@ -853,13 +886,34 @@ static int tpm_emulator_pre_save(void *opaque)
 {
     TPMBackend *tb = opaque;
     TPMEmulator *tpm_emu = TPM_EMULATOR(tb);
+    int ret;
 
     trace_tpm_emulator_pre_save();
 
     tpm_backend_finish_sync(tb);
 
     /* get the state blobs from the TPM */
-    return tpm_emulator_get_state_blobs(tpm_emu);
+    ret = tpm_emulator_get_state_blobs(tpm_emu);
+
+    tpm_emu->relock_storage = ret == 0;
+
+    return ret;
+}
+
+static void tpm_emulator_vm_state_change(void *opaque, bool running,
+                                         RunState state)
+{
+    TPMBackend *tb = opaque;
+    TPMEmulator *tpm_emu = TPM_EMULATOR(tb);
+
+    trace_tpm_emulator_vm_state_change(running, state);
+
+    if (!running || state != RUN_STATE_RUNNING || !tpm_emu->relock_storage) {
+        return;
+    }
+
+    /* lock storage after migration fall-back */
+    tpm_emulator_lock_storage(tpm_emu);
 }
 
 /*
@@ -921,6 +975,9 @@ static void tpm_emulator_inst_init(Object *obj)
     tpm_emu->options = g_new0(TPMEmulatorOptions, 1);
     tpm_emu->cur_locty_number = ~0;
     qemu_mutex_init(&tpm_emu->mutex);
+    tpm_emu->vmstate =
+        qemu_add_vm_change_state_handler(tpm_emulator_vm_state_change,
+                                         tpm_emu);
 
     vmstate_register(NULL, VMSTATE_INSTANCE_ID_ANY,
                      &vmstate_tpm_emulator, obj);
@@ -970,6 +1027,7 @@ static void tpm_emulator_inst_finalize(Object *obj)
     tpm_sized_buffer_reset(&state_blobs->savestate);
 
     qemu_mutex_destroy(&tpm_emu->mutex);
+    qemu_del_vm_change_state_handler(tpm_emu->vmstate);
 
     vmstate_unregister(NULL, &vmstate_tpm_emulator, obj);
 }
diff --git a/backends/tpm/trace-events b/backends/tpm/trace-events
index 3298766dd7..1ecef42a07 100644
--- a/backends/tpm/trace-events
+++ b/backends/tpm/trace-events
@@ -20,6 +20,8 @@ tpm_emulator_set_buffer_size(uint32_t buffersize, uint32_t minsize, uint32_t max
 tpm_emulator_startup_tpm_resume(bool is_resume, size_t buffersize) "is_resume: %d, buffer size: %zu"
 tpm_emulator_get_tpm_established_flag(uint8_t flag) "got established flag: %d"
 tpm_emulator_cancel_cmd_not_supt(void) "Backend does not support CANCEL_TPM_CMD"
+tpm_emulator_lock_storage_cmd_not_supt(void) "Backend does not support LOCK_STORAGE"
+tpm_emulator_vm_state_change(int running, int state) "state change to running %d state %d"
 tpm_emulator_handle_device_opts_tpm12(void) "TPM Version 1.2"
 tpm_emulator_handle_device_opts_tpm2(void) "TPM Version 2"
 tpm_emulator_handle_device_opts_unspec(void) "TPM Version Unspecified"