xen/mem_event: Cleanup of mem_event structures

The public mem_event structures used to communicate with helper applications via
shared rings have been are used in different settings. However, the variable names
within this structure have not reflected this fact, resulting in the reuse of
variables to mean different things under different scenarios.

This patch remedies the issue by clearly defining the structure members based on
the actual context within which the structure is used.

Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
xen/mem_event: Rename the mem_event ring from 'access' to 'monitor'

The name of the ring still implies it is used only for memory accesses,
which is no longer the case. It is also used to deliver variuos HVM events,
thus the name "monitor" is more appropriate in this setting.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
xen/mem_paging: Convert mem_event_op to mem_paging_op

The only use-case of the mem_event_op structure had been in mem_paging,
thus renaming the structure mem_paging_op and relocating its associated
functions clarifies its actual usage.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
x86/hvm: rename hvm_memory_event_* functions to hvm_event_*

The function names currently imply that these events are to be delivered via
the memory_event subsystem. However, the naming is confusing as these events
have nothing to do with actual memory events. Simply naming these functions
hvm_event_* more accurately describe their usage.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
xen/mem_event: Rename mem_event to vm_event

The mem_event system has originally been used to deliver memory event
related information to helper programs located in a domain. However,
the usage of this sub-system have since been expanded to include non-memory
related events as well, such as register changes, debugging and singlestepping.
Therefore, renaming the system "vm_event" more accurately describes the actual
usage of the subsystem.

In this patch I also clear up the ambiguities that resulted from the interchanged
mem_event and mem_access terminology.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@zentific.com>
tools/tests: Remove superfluous and incomplete spinlock from xen-access