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diff --git a/include/qapi/error.h b/include/qapi/error.h
new file mode 100644
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--- /dev/null
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@@ -0,0 +1,534 @@
+/*
+ * QEMU Error Objects
+ *
+ * Copyright IBM, Corp. 2011
+ * Copyright (C) 2011-2015 Red Hat, Inc.
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Markus Armbruster <armbru@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2.  See
+ * the COPYING.LIB file in the top-level directory.
+ */
+
+/*
+ * Error reporting system loosely patterned after Glib's GError.
+ *
+ * = Rules =
+ *
+ * - Functions that use Error to report errors have an Error **errp
+ *   parameter.  It should be the last parameter, except for functions
+ *   taking variable arguments.
+ *
+ * - You may pass NULL to not receive the error, &error_abort to abort
+ *   on error, &error_fatal to exit(1) on error, or a pointer to a
+ *   variable containing NULL to receive the error.
+ *
+ * - Separation of concerns: the function is responsible for detecting
+ *   errors and failing cleanly; handling the error is its caller's
+ *   job.  Since the value of @errp is about handling the error, the
+ *   function should not examine it.
+ *
+ * - The function may pass @errp to functions it calls to pass on
+ *   their errors to its caller.  If it dereferences @errp to check
+ *   for errors, it must use ERRP_GUARD().
+ *
+ * - On success, the function should not touch *errp.  On failure, it
+ *   should set a new error, e.g. with error_setg(errp, ...), or
+ *   propagate an existing one, e.g. with error_propagate(errp, ...).
+ *
+ * - Whenever practical, also return a value that indicates success /
+ *   failure.  This can make the error checking more concise, and can
+ *   avoid useless error object creation and destruction.  Note that
+ *   we still have many functions returning void.  We recommend
+ *   • bool-valued functions return true on success / false on failure,
+ *   • pointer-valued functions return non-null / null pointer, and
+ *   • integer-valued functions return non-negative / negative.
+ *
+ * = Creating errors =
+ *
+ * Create an error:
+ *     error_setg(errp, "situation normal, all fouled up");
+ * where @errp points to the location to receive the error.
+ *
+ * Create an error and add additional explanation:
+ *     error_setg(errp, "invalid quark");
+ *     error_append_hint(errp, "Valid quarks are up, down, strange, "
+ *                       "charm, top, bottom.\n");
+ * This may require use of ERRP_GUARD(); more on that below.
+ *
+ * Do *not* contract this to
+ *     error_setg(errp, "invalid quark\n" // WRONG!
+ *                "Valid quarks are up, down, strange, charm, top, bottom.");
+ *
+ * = Reporting and destroying errors =
+ *
+ * Report an error to the current monitor if we have one, else stderr:
+ *     error_report_err(err);
+ * This frees the error object.
+ *
+ * Likewise, but with additional text prepended:
+ *     error_reportf_err(err, "Could not frobnicate '%s': ", name);
+ *
+ * Report an error somewhere else:
+ *     const char *msg = error_get_pretty(err);
+ *     do with msg what needs to be done...
+ *     error_free(err);
+ * Note that this loses hints added with error_append_hint().
+ *
+ * Call a function ignoring errors:
+ *     foo(arg, NULL);
+ * This is more concise than
+ *     Error *err = NULL;
+ *     foo(arg, &err);
+ *     error_free(err); // don't do this
+ *
+ * Call a function aborting on errors:
+ *     foo(arg, &error_abort);
+ * This is more concise and fails more nicely than
+ *     Error *err = NULL;
+ *     foo(arg, &err);
+ *     assert(!err); // don't do this
+ *
+ * Call a function treating errors as fatal:
+ *     foo(arg, &error_fatal);
+ * This is more concise than
+ *     Error *err = NULL;
+ *     foo(arg, &err);
+ *     if (err) { // don't do this
+ *         error_report_err(err);
+ *         exit(1);
+ *     }
+ *
+ * Handle an error without reporting it (just for completeness):
+ *     error_free(err);
+ *
+ * Assert that an expected error occurred, but clean it up without
+ * reporting it (primarily useful in testsuites):
+ *     error_free_or_abort(&err);
+ *
+ * = Passing errors around =
+ *
+ * Errors get passed to the caller through the conventional @errp
+ * parameter.
+ *
+ * Create a new error and pass it to the caller:
+ *     error_setg(errp, "situation normal, all fouled up");
+ *
+ * Call a function, receive an error from it, and pass it to the caller
+ * - when the function returns a value that indicates failure, say
+ *   false:
+ *     if (!foo(arg, errp)) {
+ *         handle the error...
+ *     }
+ * - when it does not, say because it is a void function:
+ *     ERRP_GUARD();
+ *     foo(arg, errp);
+ *     if (*errp) {
+ *         handle the error...
+ *     }
+ * More on ERRP_GUARD() below.
+ *
+ * Code predating ERRP_GUARD() still exists, and looks like this:
+ *     Error *err = NULL;
+ *     foo(arg, &err);
+ *     if (err) {
+ *         handle the error...
+ *         error_propagate(errp, err); // deprecated
+ *     }
+ * Avoid in new code.  Do *not* "optimize" it to
+ *     foo(arg, errp);
+ *     if (*errp) { // WRONG!
+ *         handle the error...
+ *     }
+ * because errp may be NULL without the ERRP_GUARD() guard.
+ *
+ * But when all you do with the error is pass it on, please use
+ *     foo(arg, errp);
+ * for readability.
+ *
+ * Receive an error, and handle it locally
+ * - when the function returns a value that indicates failure, say
+ *   false:
+ *     Error *err = NULL;
+ *     if (!foo(arg, &err)) {
+ *         handle the error...
+ *     }
+ * - when it does not, say because it is a void function:
+ *     Error *err = NULL;
+ *     foo(arg, &err);
+ *     if (err) {
+ *         handle the error...
+ *     }
+ *
+ * Pass an existing error to the caller:
+ *     error_propagate(errp, err);
+ * This is rarely needed.  When @err is a local variable, use of
+ * ERRP_GUARD() commonly results in more readable code.
+ *
+ * Pass an existing error to the caller with the message modified:
+ *     error_propagate_prepend(errp, err,
+ *                             "Could not frobnicate '%s': ", name);
+ * This is more concise than
+ *     error_propagate(errp, err); // don't do this
+ *     error_prepend(errp, "Could not frobnicate '%s': ", name);
+ * and works even when @errp is &error_fatal.
+ *
+ * Receive and accumulate multiple errors (first one wins):
+ *     Error *err = NULL, *local_err = NULL;
+ *     foo(arg, &err);
+ *     bar(arg, &local_err);
+ *     error_propagate(&err, local_err);
+ *     if (err) {
+ *         handle the error...
+ *     }
+ *
+ * Do *not* "optimize" this to
+ *     Error *err = NULL;
+ *     foo(arg, &err);
+ *     bar(arg, &err); // WRONG!
+ *     if (err) {
+ *         handle the error...
+ *     }
+ * because this may pass a non-null err to bar().
+ *
+ * Likewise, do *not*
+ *     Error *err = NULL;
+ *     if (cond1) {
+ *         error_setg(&err, ...);
+ *     }
+ *     if (cond2) {
+ *         error_setg(&err, ...); // WRONG!
+ *     }
+ * because this may pass a non-null err to error_setg().
+ *
+ * = Why, when and how to use ERRP_GUARD() =
+ *
+ * Without ERRP_GUARD(), use of the @errp parameter is restricted:
+ * - It must not be dereferenced, because it may be null.
+ * - It should not be passed to error_prepend() or
+ *   error_append_hint(), because that doesn't work with &error_fatal.
+ * ERRP_GUARD() lifts these restrictions.
+ *
+ * To use ERRP_GUARD(), add it right at the beginning of the function.
+ * @errp can then be used without worrying about the argument being
+ * NULL or &error_fatal.
+ *
+ * Using it when it's not needed is safe, but please avoid cluttering
+ * the source with useless code.
+ *
+ * = Converting to ERRP_GUARD() =
+ *
+ * To convert a function to use ERRP_GUARD():
+ *
+ * 0. If the Error ** parameter is not named @errp, rename it to
+ *    @errp.
+ *
+ * 1. Add an ERRP_GUARD() invocation, by convention right at the
+ *    beginning of the function.  This makes @errp safe to use.
+ *
+ * 2. Replace &err by errp, and err by *errp.  Delete local variable
+ *    @err.
+ *
+ * 3. Delete error_propagate(errp, *errp), replace
+ *    error_propagate_prepend(errp, *errp, ...) by error_prepend(errp, ...)
+ *
+ * 4. Ensure @errp is valid at return: when you destroy *errp, set
+ *    *errp = NULL.
+ *
+ * Example:
+ *
+ *     bool fn(..., Error **errp)
+ *     {
+ *         Error *err = NULL;
+ *
+ *         foo(arg, &err);
+ *         if (err) {
+ *             handle the error...
+ *             error_propagate(errp, err);
+ *             return false;
+ *         }
+ *         ...
+ *     }
+ *
+ * becomes
+ *
+ *     bool fn(..., Error **errp)
+ *     {
+ *         ERRP_GUARD();
+ *
+ *         foo(arg, errp);
+ *         if (*errp) {
+ *             handle the error...
+ *             return false;
+ *         }
+ *         ...
+ *     }
+ *
+ * For mass-conversion, use scripts/coccinelle/errp-guard.cocci.
+ */
+
+#ifndef ERROR_H
+#define ERROR_H
+
+#include "qapi/qapi-types-error.h"
+
+/*
+ * Overall category of an error.
+ * Based on the qapi type QapiErrorClass, but reproduced here for nicer
+ * enum names.
+ */
+typedef enum ErrorClass {
+    ERROR_CLASS_GENERIC_ERROR = QAPI_ERROR_CLASS_GENERICERROR,
+    ERROR_CLASS_COMMAND_NOT_FOUND = QAPI_ERROR_CLASS_COMMANDNOTFOUND,
+    ERROR_CLASS_DEVICE_NOT_ACTIVE = QAPI_ERROR_CLASS_DEVICENOTACTIVE,
+    ERROR_CLASS_DEVICE_NOT_FOUND = QAPI_ERROR_CLASS_DEVICENOTFOUND,
+    ERROR_CLASS_KVM_MISSING_CAP = QAPI_ERROR_CLASS_KVMMISSINGCAP,
+} ErrorClass;
+
+/*
+ * Get @err's human-readable error message.
+ */
+const char *error_get_pretty(const Error *err);
+
+/*
+ * Get @err's error class.
+ * Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
+ * strongly discouraged.
+ */
+ErrorClass error_get_class(const Error *err);
+
+/*
+ * Create a new error object and assign it to *@errp.
+ * If @errp is NULL, the error is ignored.  Don't bother creating one
+ * then.
+ * If @errp is &error_abort, print a suitable message and abort().
+ * If @errp is &error_fatal, print a suitable message and exit(1).
+ * If @errp is anything else, *@errp must be NULL.
+ * The new error's class is ERROR_CLASS_GENERIC_ERROR, and its
+ * human-readable error message is made from printf-style @fmt, ...
+ * The resulting message should be a single phrase, with no newline or
+ * trailing punctuation.
+ * Please don't error_setg(&error_fatal, ...), use error_report() and
+ * exit(), because that's more obvious.
+ * Likewise, don't error_setg(&error_abort, ...), use assert().
+ */
+#define error_setg(errp, fmt, ...)                              \
+    error_setg_internal((errp), __FILE__, __LINE__, __func__,   \
+                        (fmt), ## __VA_ARGS__)
+void error_setg_internal(Error **errp,
+                         const char *src, int line, const char *func,
+                         const char *fmt, ...)
+    GCC_FMT_ATTR(5, 6);
+
+/*
+ * Just like error_setg(), with @os_error info added to the message.
+ * If @os_error is non-zero, ": " + strerror(os_error) is appended to
+ * the human-readable error message.
+ *
+ * The value of errno (which usually can get clobbered by almost any
+ * function call) will be preserved.
+ */
+#define error_setg_errno(errp, os_error, fmt, ...)                      \
+    error_setg_errno_internal((errp), __FILE__, __LINE__, __func__,     \
+                              (os_error), (fmt), ## __VA_ARGS__)
+void error_setg_errno_internal(Error **errp,
+                               const char *fname, int line, const char *func,
+                               int os_error, const char *fmt, ...)
+    GCC_FMT_ATTR(6, 7);
+
+#ifdef _WIN32
+/*
+ * Just like error_setg(), with @win32_error info added to the message.
+ * If @win32_error is non-zero, ": " + g_win32_error_message(win32_err)
+ * is appended to the human-readable error message.
+ */
+#define error_setg_win32(errp, win32_err, fmt, ...)                     \
+    error_setg_win32_internal((errp), __FILE__, __LINE__, __func__,     \
+                              (win32_err), (fmt), ## __VA_ARGS__)
+void error_setg_win32_internal(Error **errp,
+                               const char *src, int line, const char *func,
+                               int win32_err, const char *fmt, ...)
+    GCC_FMT_ATTR(6, 7);
+#endif
+
+/*
+ * Propagate error object (if any) from @local_err to @dst_errp.
+ * If @local_err is NULL, do nothing (because there's nothing to
+ * propagate).
+ * Else, if @dst_errp is NULL, errors are being ignored.  Free the
+ * error object.
+ * Else, if @dst_errp is &error_abort, print a suitable message and
+ * abort().
+ * Else, if @dst_errp is &error_fatal, print a suitable message and
+ * exit(1).
+ * Else, if @dst_errp already contains an error, ignore this one: free
+ * the error object.
+ * Else, move the error object from @local_err to *@dst_errp.
+ * On return, @local_err is invalid.
+ * Please use ERRP_GUARD() instead when possible.
+ * Please don't error_propagate(&error_fatal, ...), use
+ * error_report_err() and exit(), because that's more obvious.
+ */
+void error_propagate(Error **dst_errp, Error *local_err);
+
+
+/*
+ * Propagate error object (if any) with some text prepended.
+ * Behaves like
+ *     error_prepend(&local_err, fmt, ...);
+ *     error_propagate(dst_errp, local_err);
+ * Please use ERRP_GUARD() and error_prepend() instead when possible.
+ */
+void error_propagate_prepend(Error **dst_errp, Error *local_err,
+                             const char *fmt, ...)
+    GCC_FMT_ATTR(3, 4);
+
+/*
+ * Prepend some text to @errp's human-readable error message.
+ * The text is made by formatting @fmt, @ap like vprintf().
+ */
+void error_vprepend(Error *const *errp, const char *fmt, va_list ap)
+    GCC_FMT_ATTR(2, 0);
+
+/*
+ * Prepend some text to @errp's human-readable error message.
+ * The text is made by formatting @fmt, ... like printf().
+ */
+void error_prepend(Error *const *errp, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
+
+/*
+ * Append a printf-style human-readable explanation to an existing error.
+ * If the error is later reported to a human user with
+ * error_report_err() or warn_report_err(), the hints will be shown,
+ * too.  If it's reported via QMP, the hints will be ignored.
+ * Intended use is adding helpful hints on the human user interface,
+ * e.g. a list of valid values.  It's not for clarifying a confusing
+ * error message.
+ * @errp may be NULL, but not &error_fatal or &error_abort.
+ * Trivially the case if you call it only after error_setg() or
+ * error_propagate().
+ * May be called multiple times.  The resulting hint should end with a
+ * newline.
+ */
+void error_append_hint(Error *const *errp, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
+
+/*
+ * Convenience function to report open() failure.
+ */
+#define error_setg_file_open(errp, os_errno, filename)                  \
+    error_setg_file_open_internal((errp), __FILE__, __LINE__, __func__, \
+                                  (os_errno), (filename))
+void error_setg_file_open_internal(Error **errp,
+                                   const char *src, int line, const char *func,
+                                   int os_errno, const char *filename);
+
+/*
+ * Return an exact copy of @err.
+ */
+Error *error_copy(const Error *err);
+
+/*
+ * Free @err.
+ * @err may be NULL.
+ */
+void error_free(Error *err);
+
+/*
+ * Convenience function to assert that *@errp is set, then silently free it.
+ */
+void error_free_or_abort(Error **errp);
+
+/*
+ * Convenience function to warn_report() and free @err.
+ * The report includes hints added with error_append_hint().
+ */
+void warn_report_err(Error *err);
+
+/*
+ * Convenience function to error_report() and free @err.
+ * The report includes hints added with error_append_hint().
+ */
+void error_report_err(Error *err);
+
+/*
+ * Convenience function to error_prepend(), warn_report() and free @err.
+ */
+void warn_reportf_err(Error *err, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
+
+/*
+ * Convenience function to error_prepend(), error_report() and free @err.
+ */
+void error_reportf_err(Error *err, const char *fmt, ...)
+    GCC_FMT_ATTR(2, 3);
+
+/*
+ * Just like error_setg(), except you get to specify the error class.
+ * Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
+ * strongly discouraged.
+ */
+#define error_set(errp, err_class, fmt, ...)                    \
+    error_set_internal((errp), __FILE__, __LINE__, __func__,    \
+                       (err_class), (fmt), ## __VA_ARGS__)
+void error_set_internal(Error **errp,
+                        const char *src, int line, const char *func,
+                        ErrorClass err_class, const char *fmt, ...)
+    GCC_FMT_ATTR(6, 7);
+
+/*
+ * Make @errp parameter easier to use regardless of argument value
+ *
+ * This macro is for use right at the beginning of a function that
+ * takes an Error **errp parameter to pass errors to its caller.  The
+ * parameter must be named @errp.
+ *
+ * It must be used when the function dereferences @errp or passes
+ * @errp to error_prepend(), error_vprepend(), or error_append_hint().
+ * It is safe to use even when it's not needed, but please avoid
+ * cluttering the source with useless code.
+ *
+ * If @errp is NULL or &error_fatal, rewrite it to point to a local
+ * Error variable, which will be automatically propagated to the
+ * original @errp on function exit.
+ *
+ * Note: &error_abort is not rewritten, because that would move the
+ * abort from the place where the error is created to the place where
+ * it's propagated.
+ */
+#define ERRP_GUARD()                                            \
+    g_auto(ErrorPropagator) _auto_errp_prop = {.errp = errp};   \
+    do {                                                        \
+        if (!errp || errp == &error_fatal) {                    \
+            errp = &_auto_errp_prop.local_err;                  \
+        }                                                       \
+    } while (0)
+
+typedef struct ErrorPropagator {
+    Error *local_err;
+    Error **errp;
+} ErrorPropagator;
+
+static inline void error_propagator_cleanup(ErrorPropagator *prop)
+{
+    error_propagate(prop->errp, prop->local_err);
+}
+
+G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagator, error_propagator_cleanup);
+
+/*
+ * Special error destination to abort on error.
+ * See error_setg() and error_propagate() for details.
+ */
+extern Error *error_abort;
+
+/*
+ * Special error destination to exit(1) on error.
+ * See error_setg() and error_propagate() for details.
+ */
+extern Error *error_fatal;
+
+#endif