xen: Relocate mem_access and mem_event into common.

In preparation to add support for ARM LPAE mem_event, relocate mem_access,
mem_event and auxiliary functions into common Xen code.
This patch makes no functional changes to the X86 side, for ARM mem_event
and mem_access functions are just defined as placeholder stubs, and are
actually enabled later in the series.

Edits that are only header path adjustments:
   xen/arch/x86/domctl.c
   xen/arch/x86/mm/hap/nested_ept.c
   xen/arch/x86/mm/hap/nested_hap.c
   xen/arch/x86/mm/mem_paging.c
   xen/arch/x86/mm/mem_sharing.c
   xen/arch/x86/mm/p2m-pod.c
   xen/arch/x86/mm/p2m-pt.c
   xen/arch/x86/mm/p2m.c
   xen/arch/x86/x86_64/compat/mm.c
   xen/arch/x86/x86_64/mm.c

Makefile adjustments for new/removed code:
   xen/common/Makefile
   xen/arch/x86/mm/Makefile

Relocated prepare_ring_for_helper and destroy_ring_for_helper functions:
   xen/include/xen/mm.h
   xen/common/memory.c
   xen/include/asm-x86/hvm/hvm.h
   xen/arch/x86/hvm/hvm.c

Code movement of mem_event and mem_access with required ifdef wrappers
added to only compile with CONFIG_X86:
    xen/arch/x86/mm/mem_access.c -> xen/common/mem_access.c
    xen/arch/x86/mm/mem_event.c -> xen/common/mem_event.c
    xen/include/asm-x86/mem_access.h -> xen/include/xen/mem_access.h
    xen/include/asm-x86/mem_event.h -> xen/include/xen/mem_event.h

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v3: Replace asm/domain.h with xen/sched.h in mem_event.c.
v2: Update MAINTAINERS.
    More descriptive commit message to aid in the review process.
xen/mem_event: Clean out superflous white-spaces

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v2: Clean the mem_event header as well.
xen/mem_event: Relax error condition on debug builds

A faulty tool stack can brick a debug hypervisor. Unpleasant while dev/test.

Suggested-by: Andres Lagar Cavilla <andres@lagarcavilla.org>
Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
xen/mem_event: Abstract architecture specific sanity checks

Move architecture specific sanity checks into its own function
which is called when enabling mem_event.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v2: Move sanity check function into architecture specific p2m.h
xen/mem_access: Abstract architecture specific sanity check

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v2: Move sanity check function into architecture specific p2m.h
tools/libxc: Allocate magic page for mem access on ARM

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
xen/arm: p2m type definitions and changes

Define p2m_access_t in ARM and add necessary changes for page table
construction routines to pass the default access information. Also,
define the Radix tree that will hold access permission settings as
the PTE's don't have enough software programmable bits available.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
xen/arm: Add mem_event domctl and mem_access memop.

Define the handling of XEN_DOMCTL_mem_event_op and the handling of
copy-back data. Also setup the memop handling of XENMEM_access_op
with the required masking of the operation with MEMOP_CMD_MASK.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
xen/arm: Data abort exception (R/W) mem_events.

This patch enables to store, set, check and deliver LPAE R/W mem_events.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v2: - Patch been split to ease the review process.
    - Add definitions of data abort data fetch status codes (enum dabt_dfsc)
      and only call p2m_mem_access_check for traps caused by permission violations.
    - Only call p2m_write_pte in p2m_lookup if the PTE permission actually changed.
    - Properly save settings in the Radix tree and pause the VCPU with
      mem_event_vcpu_pause.
xen/arm: Instruction prefetch abort (X) mem_event handling

Add missing structure definition for iabt and update the trap handling
mechanism to only inject the exception if the mem_access checker
decides to do so.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v2: Add definition for instruction abort instruction fetch status codes (enum iabt_ifsc)
       and only call p2m_mem_access_check for traps triggered for permission violations.
xen/arm: Enable the compilation of mem_access and mem_event on ARM.

This patch sets up the infrastructure to support mem_access and mem_event
on ARM and turns on compilation. We define the required XSM functions.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v3: Wrap mem_event related functions in XSM into #ifdef HAS_MEM_ACCESS
       blocks.
    Update XSM hooks in flask to properly wire it up ARM.

v2: Add CONFIG_MEM_PAGING and CONFIG_MEM_SHARING definitions and
       use them instead of CONFIG_X86.
    Split domctl copy-back and p2m type definitions into separate
       patches and move this patch to the end of the series.
tools/tests: Enable xen-access on ARM

On ARM the guest memory doesn't start from 0, thus we include the
required headers and define GUEST_RAM_BASE_PFN in both architecture
to be passed to mem_access as the starting pfn.
We also define the ARM specific test_and_set_bit function.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>