>From 36538b4dfde5ccaa663d3d7c738fdef595027cb6 Mon Sep 17 00:00:00 2001
From: Claudio Fontana <cfontana@suse.de>
Date: Tue, 21 Jul 2020 10:10:29 +0200
Subject: [PATCH 2/2] XXX reproducer for backing file migration test issue

do not commit. During a snapshot save, this changeset throws away
all fields from the stream with the exception of "s390-skeys",
which is added as a field for all architectures (renaming the
real s390-skeys to something else).

This allows to compare the reproducibility of the snapshot
issue with all architectures.

Signed-off-by: Claudio Fontana <cfontana@suse.de>
---
 hw/s390x/s390-skeys.c |  2 +-
 migration/savevm.c    | 31 +++++++++++++++++++++++
 softmmu/cpus.c        | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 100 insertions(+), 1 deletion(-)

diff --git a/hw/s390x/s390-skeys.c b/hw/s390x/s390-skeys.c
index db2f49cb27..41116bdcc1 100644
--- a/hw/s390x/s390-skeys.c
+++ b/hw/s390x/s390-skeys.c
@@ -389,7 +389,7 @@ static inline void s390_skeys_set_migration_enabled(Object *obj, bool value,
     ss->migration_enabled = value;
 
     if (ss->migration_enabled) {
-        register_savevm_live(TYPE_S390_SKEYS, 0, 1,
+        register_savevm_live("s390-oldkeys", 0, 1,
                              &savevm_s390_storage_keys, ss);
     } else {
         unregister_savevm(VMSTATE_IF(ss), TYPE_S390_SKEYS, ss);
diff --git a/migration/savevm.c b/migration/savevm.c
index 45c9dd9d8a..b63af07ccd 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1163,6 +1163,11 @@ void qemu_savevm_state_setup(QEMUFile *f)
 
     trace_savevm_state_setup();
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
+
+        if (strcmp(se->idstr, "s390-skeys") != 0) {
+            /* only save keys */
+            continue;
+        }
         if (!se->ops || !se->ops->save_setup) {
             continue;
         }
@@ -1194,6 +1199,11 @@ int qemu_savevm_state_resume_prepare(MigrationState *s)
     trace_savevm_state_resume_prepare();
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
+
+        if (strcmp(se->idstr, "s390-skeys") != 0) {
+            /* only save keys */
+            continue;
+        }
         if (!se->ops || !se->ops->resume_prepare) {
             continue;
         }
@@ -1224,6 +1234,11 @@ int qemu_savevm_state_iterate(QEMUFile *f, bool postcopy)
 
     trace_savevm_state_iterate();
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
+
+        if (strcmp(se->idstr, "s390-skeys") != 0) {
+            /* only save keys */
+            continue;
+        }
         if (!se->ops || !se->ops->save_live_iterate) {
             continue;
         }
@@ -1325,6 +1340,12 @@ int qemu_savevm_state_complete_precopy_iterable(QEMUFile *f, bool in_postcopy)
     int ret;
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
+
+        if (strcmp(se->idstr, "s390-skeys") != 0) {
+            /* only save keys */
+            continue;
+        }
+
         if (!se->ops ||
             (in_postcopy && se->ops->has_postcopy &&
              se->ops->has_postcopy(se->opaque)) ||
@@ -1368,6 +1389,11 @@ int qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
     json_start_array(vmdesc, "devices");
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
 
+        if (strcmp(se->idstr, "s390-skeys") != 0) {
+            /* only save keys */
+            continue;
+        }
+
         if ((!se->ops || !se->ops->save_state) && !se->vmsd) {
             continue;
         }
@@ -1583,6 +1609,11 @@ int qemu_save_device_state(QEMUFile *f)
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         int ret;
 
+        if (strcmp(se->idstr, "s390-skeys") != 0) {
+            /* only save keys */
+            continue;
+        }
+
         if (se->is_ram) {
             continue;
         }
diff --git a/softmmu/cpus.c b/softmmu/cpus.c
index a802e899ab..ae3ad0878c 100644
--- a/softmmu/cpus.c
+++ b/softmmu/cpus.c
@@ -63,6 +63,9 @@
 
 #include "sysemu/cpu-throttle.h"
 
+#include "migration/qemu-file-types.h"
+#include "migration/register.h"
+
 #ifdef CONFIG_LINUX
 
 #include <sys/prctl.h>
@@ -732,11 +735,76 @@ static const VMStateDescription vmstate_timers = {
     }
 };
 
+static void s390_storage_keys_save(QEMUFile *f, void *opaque)
+{
+    uint64_t eos = 1, data = 2;
+    uint8_t *buf;
+
+    buf = g_try_malloc(32768);
+    if (!buf) {
+        error_report("storage key save could not allocate memory");
+        goto end_stream;
+    }
+
+    qemu_put_be64(f, data);
+    qemu_put_be64(f, 32768);
+
+    memset(buf, 0, 32768);
+    qemu_put_buffer(f, buf, 32768);
+    g_free(buf);
+
+ end_stream:
+    qemu_put_be64(f, eos);
+}
+
+static int s390_storage_keys_load(QEMUFile *f, void *opaque, int version_id)
+{
+    int ret = 0;
+    uint64_t data;
+    uint8_t *buf;
+
+    while (ret == 0) {
+        data = qemu_get_be64(f);
+
+        switch (data) {
+        case 2: {
+            const uint64_t total_count = qemu_get_be64(f);
+            buf = g_try_malloc(32768);
+            if (!buf) {
+                error_report("storage key load could not allocate memory");
+                ret = -ENOMEM;
+                break;
+            }
+            qemu_get_buffer(f, buf, total_count);
+            g_free(buf);
+            break;
+        }
+        case 1: {
+            /* normal exit */
+            return 0;
+        }
+        default:
+            error_report("Unexpected storage key data: %#lx", data);
+            ret = -EINVAL;
+        }
+    }
+    return ret;
+}
+
+static SaveVMHandlers savevm_s390_storage_keys = {
+    .save_state = s390_storage_keys_save,
+    .load_state = s390_storage_keys_load,
+};
+
 void cpu_ticks_init(void)
 {
     seqlock_init(&timers_state.vm_clock_seqlock);
     qemu_spin_init(&timers_state.vm_clock_lock);
     vmstate_register(NULL, 0, &vmstate_timers, &timers_state);
+
+    register_savevm_live("s390-skeys", 0, 1,
+                         &savevm_s390_storage_keys, NULL);
+
     cpu_throttle_init();
 }
 
-- 
2.16.4