- Introduce a new post_load_with_error() hook that will
  take in the Error object as a parameter.
- This error object is set if the loading of state fails.
- The error can then be retrieved using QMP command
  {"execute" : "query-migrate"}

Buglink: https://issues.redhat.com/browse/RHEL-82826

Signed-off-by: Arun Menon <arme...@redhat.com>
---
 backends/tpm/tpm_emulator.c | 39 ++++++++++++++++++++-------------------
 include/migration/vmstate.h |  1 +
 migration/vmstate.c         |  4 +++-
 3 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
index 
4a234ab2c0b19b2604bf0dd8cb5f4540c72a9438..816134d7b4de00a75a3d0b928d160595b17be810
 100644
--- a/backends/tpm/tpm_emulator.c
+++ b/backends/tpm/tpm_emulator.c
@@ -819,7 +819,8 @@ static int tpm_emulator_get_state_blobs(TPMEmulator 
*tpm_emu)
 static int tpm_emulator_set_state_blob(TPMEmulator *tpm_emu,
                                        uint32_t type,
                                        TPMSizedBuffer *tsb,
-                                       uint32_t flags)
+                                       uint32_t flags,
+                                       Error **errp)
 {
     ssize_t n;
     ptm_setstate pss;
@@ -838,17 +839,17 @@ static int tpm_emulator_set_state_blob(TPMEmulator 
*tpm_emu,
     /* write the header only */
     if (tpm_emulator_ctrlcmd(tpm_emu, CMD_SET_STATEBLOB, &pss,
                              offsetof(ptm_setstate, u.req.data), 0, 0) < 0) {
-        error_report("tpm-emulator: could not set state blob type %d : %s",
-                     type, strerror(errno));
+        error_setg(errp, "tpm-emulator: could not set state blob type %d : %s",
+                   type, strerror(errno));
         return -1;
     }
 
     /* now the body */
     n = qemu_chr_fe_write_all(&tpm_emu->ctrl_chr, tsb->buffer, tsb->size);
     if (n != tsb->size) {
-        error_report("tpm-emulator: Writing the stateblob (type %d) "
-                     "failed; could not write %u bytes, but only %zd",
-                     type, tsb->size, n);
+        error_setg(errp, "tpm-emulator: Writing the stateblob (type %d) "
+                   "failed; could not write %u bytes, but only %zd",
+                   type, tsb->size, n);
         return -1;
     }
 
@@ -856,17 +857,17 @@ static int tpm_emulator_set_state_blob(TPMEmulator 
*tpm_emu,
     n = qemu_chr_fe_read_all(&tpm_emu->ctrl_chr,
                              (uint8_t *)&pss, sizeof(pss.u.resp));
     if (n != sizeof(pss.u.resp)) {
-        error_report("tpm-emulator: Reading response from writing stateblob "
-                     "(type %d) failed; expected %zu bytes, got %zd", type,
-                     sizeof(pss.u.resp), n);
+        error_setg(errp, "tpm-emulator: Reading response from writing "
+                   "stateblob (type %d) failed; expected %zu bytes, "
+                   "got %zd", type, sizeof(pss.u.resp), n);
         return -1;
     }
 
     tpm_result = be32_to_cpu(pss.u.resp.tpm_result);
     if (tpm_result != 0) {
-        error_report("tpm-emulator: Setting the stateblob (type %d) failed "
-                     "with a TPM error 0x%x %s", type, tpm_result,
-                     tpm_emulator_strerror(tpm_result));
+        error_setg(errp, "tpm-emulator: Setting the stateblob (type %d) "
+                   "failed with a TPM error 0x%x %s", type, tpm_result,
+                   tpm_emulator_strerror(tpm_result));
         return -1;
     }
 
@@ -880,7 +881,7 @@ static int tpm_emulator_set_state_blob(TPMEmulator *tpm_emu,
  *
  * Returns a negative errno code in case of error.
  */
-static int tpm_emulator_set_state_blobs(TPMBackend *tb)
+static int tpm_emulator_set_state_blobs(TPMBackend *tb, Error **errp)
 {
     TPMEmulator *tpm_emu = TPM_EMULATOR(tb);
     TPMBlobBuffers *state_blobs = &tpm_emu->state_blobs;
@@ -894,13 +895,13 @@ static int tpm_emulator_set_state_blobs(TPMBackend *tb)
 
     if (tpm_emulator_set_state_blob(tpm_emu, PTM_BLOB_TYPE_PERMANENT,
                                     &state_blobs->permanent,
-                                    state_blobs->permanent_flags) < 0 ||
+                                    state_blobs->permanent_flags, errp) < 0 ||
         tpm_emulator_set_state_blob(tpm_emu, PTM_BLOB_TYPE_VOLATILE,
                                     &state_blobs->volatil,
-                                    state_blobs->volatil_flags) < 0 ||
+                                    state_blobs->volatil_flags, errp) < 0 ||
         tpm_emulator_set_state_blob(tpm_emu, PTM_BLOB_TYPE_SAVESTATE,
                                     &state_blobs->savestate,
-                                    state_blobs->savestate_flags) < 0) {
+                                    state_blobs->savestate_flags, errp) < 0) {
         return -EIO;
     }
 
@@ -948,12 +949,12 @@ static void tpm_emulator_vm_state_change(void *opaque, 
bool running,
  *
  * Returns negative errno codes in case of error.
  */
-static int tpm_emulator_post_load(void *opaque, int version_id)
+static int tpm_emulator_post_load(void *opaque, int version_id, Error **errp)
 {
     TPMBackend *tb = opaque;
     int ret;
 
-    ret = tpm_emulator_set_state_blobs(tb);
+    ret = tpm_emulator_set_state_blobs(tb, errp);
     if (ret < 0) {
         return ret;
     }
@@ -969,7 +970,7 @@ static const VMStateDescription vmstate_tpm_emulator = {
     .name = "tpm-emulator",
     .version_id = 0,
     .pre_save = tpm_emulator_pre_save,
-    .post_load = tpm_emulator_post_load,
+    .post_load_with_error = tpm_emulator_post_load,
     .fields = (const VMStateField[]) {
         VMSTATE_UINT32(state_blobs.permanent_flags, TPMEmulator),
         VMSTATE_UINT32(state_blobs.permanent.size, TPMEmulator),
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 
056781b1c21e737583f081594d9f88b32adfd674..1c6e89c3b08a3914cde6dce3be5955978b6b7d0b
 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -207,6 +207,7 @@ struct VMStateDescription {
     MigrationPriority priority;
     int (*pre_load)(void *opaque);
     int (*post_load)(void *opaque, int version_id);
+    int (*post_load_with_error)(void *opaque, int version_id, Error **errp);
     int (*pre_save)(void *opaque);
     int (*post_save)(void *opaque);
     bool (*needed)(void *opaque);
diff --git a/migration/vmstate.c b/migration/vmstate.c
index 
3f8c3d3c1dcfe14d70bab1f43b827244eb4bb385..c5dfffd9bad7285e819d4769e055d47157caab34
 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -232,7 +232,9 @@ int vmstate_load_state(QEMUFile *f, const 
VMStateDescription *vmsd,
         qemu_file_set_error(f, ret);
         return ret;
     }
-    if (vmsd->post_load) {
+    if (vmsd->post_load_with_error) {
+        ret = vmsd->post_load_with_error(opaque, version_id, errp);
+    } else if (vmsd->post_load) {
         ret = vmsd->post_load(opaque, version_id);
     }
     trace_vmstate_load_state_end(vmsd->name, "end", ret);

-- 
2.49.0


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