Hello all,
with the latest master branch of Xen there is a regression enabling
vm_event on a domain. If an event listener was previously active on the
domain it is now not possible to reenable events as the domctl returns
-EINVAL. The problem seems to stem from activating the magic page for
vm_event using prepare_ring_for_helper as it returns NULL. Further looking
into where things go wrong within that function it seems the page type
returned by __get_gfn_type_access is p2m_ram_logdirty with an invalid mfn
(0xffffffffffffffff) and then it hits "Error path: not a suitable GFN at
all".

Can anyone point me to which change or what may be causing this?

Thanks,
Tamas