selftests/mm: add support for arm64 platform on va switch

selftests/mm: add support for arm64 platform on va switch

Patch series "selftests/mm: Implement support for arm64 on va".

The va_128TBswitch selftest is designed and implemented for PowerPC and
x86 architectures which support a 128TB switch, up to 256TB of virtual
address space and hugepage sizes of 16MB and 2MB respectively.  Arm64
platforms on the other hand support a 256Tb switch, up to 4PB of virtual
address space and a default hugepage size of 512MB when 64k pagesize is
enabled.

These architectural differences require introducing support for arm64
platforms, after which a more generic naming convention is suggested.  The
in code comments are amended to provide a more platform independent
explanation of the working of the code and nr_hugepages are configured as
required.  Finally, the file running the testcase is modified in order to
prevent skipping of hugetlb testcases of va_high_addr_switch.

This patch (of 5):

Arm64 platforms have the ability to support 64kb pagesize, 512MB default
hugepage size and up to 4PB of virtual address space.  The address switch
occurs at 256TB as opposed to 128TB.  Hence, the necessary support has
been added.

Link: https://lkml.kernel.org/r/20230323105243.2807166-1-chaitanyas.prakash@arm.com
Link: https://lkml.kernel.org/r/20230323105243.2807166-2-chaitanyas.prakash@arm.com
Signed-off-by: Chaitanya S Prakash <chaitanyas.prakash@arm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>