arm64/mm: define arch_get_mappable_range()

This overrides arch_get_mappable_range() on arm64 platform which will be
used with recently added generic framework.  It drops
inside_linear_region() and subsequent check in arch_add_memory() which are
no longer required.  It also adds a VM_BUG_ON() check that would ensure
that mhp_range_allowed() has already been called.

Link: https://lkml.kernel.org/r/1612149902-7867-3-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: teawater <teawaterz@linux.alibaba.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm64/mm/mmu.c

@@ -1444,16 +1444,19 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size)
 	free_empty_tables(start, end, PAGE_OFFSET, PAGE_END);
 }
 
-static bool inside_linear_region(u64 start, u64 size)
+struct range arch_get_mappable_range(void)
 {
+	struct range mhp_range;
+
 	/*
 	 * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)]
 	 * accommodating both its ends but excluding PAGE_END. Max physical
 	 * range which can be mapped inside this linear mapping range, must
 	 * also be derived from its end points.
 	 */
-	return start >= __pa(_PAGE_OFFSET(vabits_actual)) &&
-	       (start + size - 1) <= __pa(PAGE_END - 1);
+	mhp_range.start = __pa(_PAGE_OFFSET(vabits_actual));
+	mhp_range.end =  __pa(PAGE_END - 1);
+	return mhp_range;
 }
 
 int arch_add_memory(int nid, u64 start, u64 size,
@@ -1461,11 +1464,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
 {
 	int ret, flags = 0;
 
-	if (!inside_linear_region(start, size)) {
-		pr_err("[%llx %llx] is outside linear mapping region\n", start, start + size);
-		return -EINVAL;
-	}
-
+	VM_BUG_ON(!mhp_range_allowed(start, size, true));
 	if (rodata_full || debug_pagealloc_enabled())
 		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;