qemu/include/hw/xen/xen-backend.h
David Woodhouse eb6ae7a682 hw/xen: do not repeatedly try to create a failing backend device
If xen_backend_device_create() fails to instantiate a device, the XenBus
code will just keep trying over and over again each time the bus is
re-enumerated, as long as the backend appears online and in
XenbusStateInitialising.

The only thing which prevents the XenBus code from recreating duplicates
of devices which already exist, is the fact that xen_device_realize()
sets the backend state to XenbusStateInitWait. If the attempt to create
the device doesn't get *that* far, that's when it will keep getting
retried.

My first thought was to handle errors by setting the backend state to
XenbusStateClosed, but that doesn't work for XenConsole which wants to
*ignore* any device of type != "ioemu" completely.

So, make xen_backend_device_create() *keep* the XenBackendInstance for a
failed device, and provide a new xen_backend_exists() function to allow
xen_bus_type_enumerate() to check whether one already exists before
creating a new one.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
2023-11-07 08:54:20 +00:00

42 lines
1.4 KiB
C

/*
* Copyright (c) 2018 Citrix Systems Inc.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef HW_XEN_BACKEND_H
#define HW_XEN_BACKEND_H
#include "hw/xen/xen-bus.h"
typedef struct XenBackendInstance XenBackendInstance;
typedef void (*XenBackendDeviceCreate)(XenBackendInstance *backend,
QDict *opts, Error **errp);
typedef void (*XenBackendDeviceDestroy)(XenBackendInstance *backend,
Error **errp);
typedef struct XenBackendInfo {
const char *type;
XenBackendDeviceCreate create;
XenBackendDeviceDestroy destroy;
} XenBackendInfo;
XenBus *xen_backend_get_bus(XenBackendInstance *backend);
const char *xen_backend_get_name(XenBackendInstance *backend);
void xen_backend_set_device(XenBackendInstance *backend,
XenDevice *xendevice);
XenDevice *xen_backend_get_device(XenBackendInstance *backend);
void xen_backend_register(const XenBackendInfo *info);
const char **xen_backend_get_types(unsigned int *nr);
bool xen_backend_exists(const char *type, const char *name);
void xen_backend_device_create(XenBus *xenbus, const char *type,
const char *name, QDict *opts, Error **errp);
bool xen_backend_try_device_destroy(XenDevice *xendev, Error **errp);
#endif /* HW_XEN_BACKEND_H */