x86/mem_access: fix vm_event emulation check with altp2m enabled

x86/mem_access: fix vm_event emulation check with altp2m enabled

Currently, p2m_mem_access_emulate_check() uses p2m_get_mem_access()
to check if the page restrictions have been lifted between the time
of sending the vm_event out and the reception of the reply - in
which case emulation is no longer required. Unfortunately,
p2m_get_mem_access() uses p2m_get_hostp2m(d) which only checks the
default EPT (view 0 in altp2m parlance). This patch fixes this by
checking the active altp2m view instead, whenever applicable.

Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>