diff --git a/block.c b/block.c
index e9f40dc768..53a978acbe 100644
--- a/block.c
+++ b/block.c
@@ -1795,8 +1795,7 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
 
     ret = bdrv_flush(reopen_state->bs);
     if (ret) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR, "Error (%s) flushing drive",
-                  strerror(-ret));
+        error_setg_errno(errp, -ret, "Error flushing drive");
         goto error;
     }
 
diff --git a/docs/writing-qmp-commands.txt b/docs/writing-qmp-commands.txt
index 8647cac4e7..59aa77ae25 100644
--- a/docs/writing-qmp-commands.txt
+++ b/docs/writing-qmp-commands.txt
@@ -210,7 +210,7 @@ if you don't see these strings, then something went wrong.
 === Errors ===
 
 QMP commands should use the error interface exported by the error.h header
-file. Basically, errors are set by calling the error_set() function.
+file. Basically, most errors are set by calling the error_setg() function.
 
 Let's say we don't accept the string "message" to contain the word "love". If
 it does contain it, we want the "hello-world" command to return an error:
@@ -219,8 +219,7 @@ void qmp_hello_world(bool has_message, const char *message, Error **errp)
 {
     if (has_message) {
         if (strstr(message, "love")) {
-            error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                      "the word 'love' is not allowed");
+            error_setg(errp, "the word 'love' is not allowed");
             return;
         }
         printf("%s\n", message);
@@ -229,10 +228,8 @@ void qmp_hello_world(bool has_message, const char *message, Error **errp)
     }
 }
 
-The first argument to the error_set() function is the Error pointer to pointer,
-which is passed to all QMP functions. The second argument is a ErrorClass
-value, which should be ERROR_CLASS_GENERIC_ERROR most of the time (more
-details about error classes are given below). The third argument is a human
+The first argument to the error_setg() function is the Error pointer
+to pointer, which is passed to all QMP functions. The next argument is a human
 description of the error, this is a free-form printf-like string.
 
 Let's test the example above. Build qemu, run it as defined in the "Testing"
@@ -249,8 +246,9 @@ The QMP server's response should be:
     }
 }
 
-As a general rule, all QMP errors should use ERROR_CLASS_GENERIC_ERROR. There
-are two exceptions to this rule:
+As a general rule, all QMP errors should use ERROR_CLASS_GENERIC_ERROR
+(done by default when using error_setg()). There are two exceptions to
+this rule:
 
  1. A non-generic ErrorClass value exists* for the failure you want to report
     (eg. DeviceNotFound)
@@ -259,8 +257,8 @@ are two exceptions to this rule:
     want to report, hence you have to add a new ErrorClass value so that they
     can check for it
 
-If the failure you want to report doesn't fall in one of the two cases above,
-just report ERROR_CLASS_GENERIC_ERROR.
+If the failure you want to report falls into one of the two cases above,
+use error_set() with a second argument of an ErrorClass value.
 
  * All existing ErrorClass values are defined in the qapi-schema.json file
 
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 0cb8afd2c2..5e20e07b6f 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1795,9 +1795,9 @@ static void pc_machine_set_max_ram_below_4g(Object *obj, Visitor *v,
         return;
     }
     if (value > (1ULL << 32)) {
-        error_set(&error, ERROR_CLASS_GENERIC_ERROR,
-                  "Machine option 'max-ram-below-4g=%"PRIu64
-                  "' expects size less than or equal to 4G", value);
+        error_setg(&error,
+                   "Machine option 'max-ram-below-4g=%"PRIu64
+                   "' expects size less than or equal to 4G", value);
         error_propagate(errp, error);
         return;
     }
diff --git a/hw/net/rocker/rocker.c b/hw/net/rocker/rocker.c
index bb6fdc364d..c57f1a661a 100644
--- a/hw/net/rocker/rocker.c
+++ b/hw/net/rocker/rocker.c
@@ -101,8 +101,7 @@ RockerSwitch *qmp_query_rocker(const char *name, Error **errp)
 
     r = rocker_find(name);
     if (!r) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                  "rocker %s not found", name);
+        error_setg(errp, "rocker %s not found", name);
         return NULL;
     }
 
@@ -122,8 +121,7 @@ RockerPortList *qmp_query_rocker_ports(const char *name, Error **errp)
 
     r = rocker_find(name);
     if (!r) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                  "rocker %s not found", name);
+        error_setg(errp, "rocker %s not found", name);
         return NULL;
     }
 
diff --git a/hw/net/rocker/rocker_of_dpa.c b/hw/net/rocker/rocker_of_dpa.c
index 1ad2791965..3cf1d61fe4 100644
--- a/hw/net/rocker/rocker_of_dpa.c
+++ b/hw/net/rocker/rocker_of_dpa.c
@@ -2462,15 +2462,13 @@ RockerOfDpaFlowList *qmp_query_rocker_of_dpa_flows(const char *name,
 
     r = rocker_find(name);
     if (!r) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                  "rocker %s not found", name);
+        error_setg(errp, "rocker %s not found", name);
         return NULL;
     }
 
     w = rocker_get_world(r, ROCKER_WORLD_TYPE_OF_DPA);
     if (!w) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                  "rocker %s doesn't have OF-DPA world", name);
+        error_setg(errp, "rocker %s doesn't have OF-DPA world", name);
         return NULL;
     }
 
@@ -2597,15 +2595,13 @@ RockerOfDpaGroupList *qmp_query_rocker_of_dpa_groups(const char *name,
 
     r = rocker_find(name);
     if (!r) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                  "rocker %s not found", name);
+        error_setg(errp, "rocker %s not found", name);
         return NULL;
     }
 
     w = rocker_get_world(r, ROCKER_WORLD_TYPE_OF_DPA);
     if (!w) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                  "rocker %s doesn't have OF-DPA world", name);
+        error_setg(errp, "rocker %s doesn't have OF-DPA world", name);
         return NULL;
     }
 
diff --git a/qom/object.c b/qom/object.c
index fc6e161088..c0decb6e96 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1330,8 +1330,8 @@ static Object *object_resolve_link(Object *obj, const char *name,
     target = object_resolve_path_type(path, target_type, &ambiguous);
 
     if (ambiguous) {
-        error_set(errp, ERROR_CLASS_GENERIC_ERROR,
-                  "Path '%s' does not uniquely identify an object", path);
+        error_setg(errp, "Path '%s' does not uniquely identify an object",
+                   path);
     } else if (!target) {
         target = object_resolve_path(path, &ambiguous);
         if (target || ambiguous) {