mm/hugetlb: enable bootmem allocation from CMA areas

If hugetlb_cma_only is enabled, we know that hugetlb pages can only be
allocated from CMA.  Now that there is an interface to do early
reservations from a CMA area (returning memblock memory), it can be used
to allocate hugetlb pages from CMA.

This also allows for doing pre-HVO on these pages (if enabled).

Make sure to initialize the page structures and associated data correctly.
Create a flag to signal that a hugetlb page has been allocated from CMA
to make things a little easier.

Some configurations of powerpc have a special hugetlb bootmem allocator,
so introduce a boolean arch_specific_huge_bootmem_alloc that returns true
if such an allocator is present.  In that case, CMA bootmem allocations
can't be used, so check that function before trying.

Link: https://lkml.kernel.org/r/20250228182928.2645936-27-fvdl@google.com


Signed-off-by: Frank van der Linden <fvdl@google.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>