docs/devel: document query handle lifetimes

I forgot to document the lifetime of handles in the developer
documentation. Do so now.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Robert Foley <robert.foley@linaro.org>
Reviewed-by: Robert Foley <robert.foley@linaro.org>
Message-Id: <20200225124710.14152-11-alex.bennee@linaro.org>

1 files changed, 11 insertions, 2 deletions

diff --git a/docs/devel/tcg-plugins.rst b/docs/devel/tcg-plugins.rst
index 718eef0..a059909 100644
--- a/docs/devel/tcg-plugins.rst
+++ b/docs/devel/tcg-plugins.rst
@@ -51,8 +51,17 @@ about how QEMU's translation works to the plugins. While there are
 conceptions such as translation time and translation blocks the
 details are opaque to plugins. The plugin is able to query select
 details of instructions and system configuration only through the
-exported *qemu_plugin* functions. The types used to describe
-instructions and events are opaque to the plugins themselves.
+exported *qemu_plugin* functions.
+
+Query Handle Lifetime
+---------------------
+
+Each callback provides an opaque anonymous information handle which
+can usually be further queried to find out information about a
+translation, instruction or operation. The handles themselves are only
+valid during the lifetime of the callback so it is important that any
+information that is needed is extracted during the callback and saved
+by the plugin.
 
 Usage
 =====