vmstate: error hint for failed equal checks

In some cases a failing VMSTATE_*_EQUAL does not mean we detected a bug,
but it's actually the best we can do. Especially in these cases a verbose
error message is required.

Let's introduce infrastructure for specifying a error hint to be used if
equal check fails. Let's do this by adding a parameter to the _EQUAL
macros called _err_hint. Also change all current users to pass NULL as
last parameter so nothing changes for them.

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>

Message-Id: <20170623144823.42936-1-pasic@linux.vnet.ibm.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index 02f05a3359..c056c98bdb 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -126,6 +126,9 @@ static int get_int32_equal(QEMUFile *f, void *pv, size_t size,
         return 0;
     }
     error_report("%" PRIx32 " != %" PRIx32, *v, v2);
+    if (field->err_hint) {
+        error_printf("%s\n", field->err_hint);
+    }
     return -EINVAL;
 }
 
@@ -267,6 +270,9 @@ static int get_uint32_equal(QEMUFile *f, void *pv, size_t size,
         return 0;
     }
     error_report("%" PRIx32 " != %" PRIx32, *v, v2);
+    if (field->err_hint) {
+        error_printf("%s\n", field->err_hint);
+    }
     return -EINVAL;
 }
 
@@ -341,6 +347,9 @@ static int get_uint64_equal(QEMUFile *f, void *pv, size_t size,
         return 0;
     }
     error_report("%" PRIx64 " != %" PRIx64, *v, v2);
+    if (field->err_hint) {
+        error_printf("%s\n", field->err_hint);
+    }
     return -EINVAL;
 }
 
@@ -364,6 +373,9 @@ static int get_uint8_equal(QEMUFile *f, void *pv, size_t size,
         return 0;
     }
     error_report("%x != %x", *v, v2);
+    if (field->err_hint) {
+        error_printf("%s\n", field->err_hint);
+    }
     return -EINVAL;
 }
 
@@ -387,6 +399,9 @@ static int get_uint16_equal(QEMUFile *f, void *pv, size_t size,
         return 0;
     }
     error_report("%x != %x", *v, v2);
+    if (field->err_hint) {
+        error_printf("%s\n", field->err_hint);
+    }
     return -EINVAL;
 }