xen/arm: Data abort exception (R/W) mem_events.

This patch enables to store, set, check and deliver LPAE R/W mem_events.
As the LPAE PTE's lack enough available software programmable bits,
we store the permissions in a Radix tree. A custom boolean, access_in_use,
specifies if the tree is in use to avoid unecessary lookups on an empty tree.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v11: - Move including common/mem_event.h in here in p2m.h.
     - Flush the tlb in p2m_set_mem_access to cover both the preemption
       and successful finish cases.
v10: - Remove ASSERT from MEMACCESS case.
    - Flush the tlb in the MEMACCESS case as we progress.
    - Typos and style fixes.
v8: - Revert to arch specific p2m_mem_access_check.
    - Retire dabt_dfsc enum and use FSC_FLT defines.
    - Revert to Radix tree approach and use access_in_use flag to
      indicate if the tree is in use or not to avoid uneccessary lookups.
v7: - Removed p2m_shatter_page and p2m_set_permission into separate
      patch.
    - Replace Radix tree settings store with extended struct page_info
      approach. This way the trap handlers can use the MMU directly to
      locate the permission store instead of having to do a tree-lookup.
    - Add p2m_get_entry/set_entry compat functions which are required by
      the common mem_access_check function.
    - Typo fixes.
v6: - Add helper function p2m_shatter_page.
    - Only allocate 4k pages when mem_access is in use.
    - If no setting was found in radix tree but PTE exists,
      return rwx as permission.
    - Move the inclusion of various headers into this patch.
    - Make npfec a const.
v5: - Move p2m_set_entry's logic into apply_one_level via
      a new p2m_op, MEMACCESS.
v4: - Add p2m_mem_access_radix_set function to be called
      when inserting new PTE's and when updating existing entries.
    - Switch p2m_mem_access_check to return bool_t.
    - Use new struct npfec to pass violation info.
v3: - Add new function for updating the PTE entries, p2m_set_entry.
    - Use the new struct npfec to pass violation information.
    - Implement n2rwx, rx2rw and listener required routines.
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: Allow hypervisor access to mem_access protected pages

The guestcopy helpers use the MMU to verify that the given guest has read/write
access to a given page during hypercalls. As we may have custom mem_access
permissions set on these pages, we do a software-based type checking in case
the MMU based approach failed, but only if access_in_use is set.

These memory accesses are not forwarded to the mem_event listener. Accesses
performed by the hypervisor are currently not part of the mem_access scheme.
This is consistent behaviour with the x86 side as well.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
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>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---
v10: - Minor comment fix for describing s1ptw.
v8: - Revert to arch specific p2m_mem_access_check.
    - Retire iabt_fsc enum and use FSC_FLT instead.
    - Complete the struct definition of hsr_iabt.
v7: - Use the new common mem_access_check.
v6: - Make npfec a const.
v4: - Don't mark instruction fetch violation as read violation.
    - Use new struct npfec to pass violation info.
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>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Julien Grall <julien.grall@linaro.org>
---
v8: All MEM_* flags have been converted to HAS_* and moved into config/*.mk

v3: Wrap mem_event related functions in XSM into #ifdef HAS_MEM_ACCESS
       blocks.
    Update XSM hooks in flask to properly wire it up on 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/libxc: Allocate magic page for mem access on ARM

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
Reviewed-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
tools/tests: Enable xen-access on ARM

Define the ARM specific test_and_set_bit functions and switch
to use maximum gpfn as the limit to setting permissions. Also,
move HAS_MEM_ACCESS definition into config.

Signed-off-by: Tamas K Lengyel <tklengyel@sec.in.tum.de>
---
v6: - Just use xc_domain_maximum_gpfn to get max_gpfn.
v5: - Use the new information returned by getdomaininfo, max_gpfn, to
      set access permissions. On ARM this will include the potential
      memory hole as well which the hypervisor just loops over.
v4: - Take into account multiple guest ram banks on ARM.
    - Move HAS_MEM_ACCESS definition into config/*.mk and only compile
      xen-access when it is defined.
    - Pass CONFIG_X86/CONFIG_ARM flags during compilation in xen-access
      Makefile.