diff options
| -rw-r--r-- | docs/qapi-code-gen.txt | 11 | ||||
| -rw-r--r-- | qapi/introspect.json | 9 |
2 files changed, 20 insertions, 0 deletions
diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt index f9fa6f3d96..ceb9a782d0 100644 --- a/docs/qapi-code-gen.txt +++ b/docs/qapi-code-gen.txt @@ -514,6 +514,17 @@ exactly the server (QEMU) supports. For this purpose, QMP provides introspection via command query-qmp-schema. QGA currently doesn't support introspection. +While Client JSON Protocol wire compatibility should be maintained +between qemu versions, we cannot make the same guarantees for +introspection stability. For example, one version of qemu may provide +a non-variant optional member of a struct, and a later version rework +the member to instead be non-optional and associated with a variant. +Likewise, one version of qemu may list a member with open-ended type +'str', and a later version could convert it to a finite set of strings +via an enum type; or a member may be converted from a specific type to +an alternate that represents a choice between the original type and +something else. + query-qmp-schema returns a JSON array of SchemaInfo objects. These objects together describe the wire ABI, as defined in the QAPI schema. There is no specified order to the SchemaInfo objects returned; a diff --git a/qapi/introspect.json b/qapi/introspect.json index e7c4c3e998..9e9369e160 100644 --- a/qapi/introspect.json +++ b/qapi/introspect.json @@ -22,6 +22,15 @@ # what's there), not interface specification. The specification is in # the QAPI schema. # +# Furthermore, while we strive to keep the QMP wire format +# backwards-compatible across qemu versions, the introspection output +# is not guaranteed to have the same stability. For example, one +# version of qemu may list an object member as an optional +# non-variant, while another lists the same member only through the +# object's variants; or the type of a member may change from a generic +# string into a specific enum or from one specific type into an +# alternate that includes the original type alongside something else. +# # Returns: array of @SchemaInfo, where each element describes an # entity in the ABI: command, event, type, ... # |