drivers/xen: Improve the late XenStore init protocol

drivers/xen: Improve the late XenStore init protocol

Currently, the late XenStore init protocol is only triggered properly
for the case that HVM_PARAM_STORE_PFN is ~0ULL (invalid). For the
case that XenStore interface is allocated but not ready (the connection
status is not XENSTORE_CONNECTED), Linux should also wait until the
XenStore is set up properly.

Introduce a macro to describe the XenStore interface is ready, use
it in xenbus_probe_initcall() to select the code path of doing the
late XenStore init protocol or not. Since now we have more than one
condition for XenStore late init, rework the check in xenbus_probe()
for the free_irq().

Take the opportunity to enhance the check of the allocated XenStore
interface can be properly mapped, and return error early if the
memremap() fails.

Fixes: 5b3353949e89 ("xen: add support for initializing xenstore later as HVM domain")
Signed-off-by: Henry Wang <[email protected]>
Signed-off-by: Michal Orzel <[email protected]>
Reviewed-by: Stefano Stabellini <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Juergen Gross <[email protected]>