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hw/xen: do not repeatedly try to create a failing backend device

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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>
This commit is contained in:
David Woodhouse 2023-10-16 10:28:17 +01:00
parent 523b6b3aba
commit eb6ae7a682
3 changed files with 24 additions and 7 deletions
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27
hw/xen/xen-backend.c
View file

@ -101,6 +101,24 @@ static XenBackendInstance *xen_backend_list_find(XenDevice *xendev)
return NULL;
}
bool xen_backend_exists(const char *type, const char *name)
{
const XenBackendImpl *impl = xen_backend_table_lookup(type);
XenBackendInstance *backend;
if (!impl) {
return false;
}
QLIST_FOREACH(backend, &backend_list, entry) {
if (backend->impl == impl && !strcmp(backend->name, name)) {
return true;
}
}
return false;
}
static void xen_backend_list_remove(XenBackendInstance *backend)
{
QLIST_REMOVE(backend, entry);
@ -122,11 +140,6 @@ void xen_backend_device_create(XenBus *xenbus, const char *type,
backend->name = g_strdup(name);
impl->create(backend, opts, errp);
if (*errp) {
g_free(backend->name);
g_free(backend);
return;
}
backend->impl = impl;
xen_backend_list_add(backend);
@ -165,7 +178,9 @@ bool xen_backend_try_device_destroy(XenDevice *xendev, Error **errp)
}
impl = backend->impl;
impl->destroy(backend, errp);
if (backend->xendev) {
impl->destroy(backend, errp);
}
xen_backend_list_remove(backend);
g_free(backend->name);