[PATCH v3 2/8] arm64: Add support for MEMBLOCK_PTEMAP

[Vincent Donnefort <vdonnefort@google.com>]

With the MEMBLOCK_PTEMAP flag, force a PTE-level mapping. This also
disables contiguous PTEs to make sure any page from the memblock can be
safely unmapped from the linear map.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
---
 arch/arm64/mm/mmu.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 140520b351e2..a4cafafa1d82 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1184,9 +1184,8 @@ static void __init map_mem(void)
 	phys_addr_t init_begin = __pa_symbol(__init_begin);
 	phys_addr_t init_end = __pa_symbol(__init_end);
 	phys_addr_t kernel_end = __pa_symbol(__bss_stop);
-	phys_addr_t start, end;
 	int flags = NO_EXEC_MAPPINGS;
-	u64 i;
+	struct memblock_region *r;
 
 	/*
 	 * Setting hierarchical PXNTable attributes on table entries covering
@@ -1226,9 +1225,14 @@ static void __init map_mem(void)
 		       flags);
 
 	/* map all the memory banks */
-	for_each_mem_range(i, &start, &end) {
+	for_each_mem_region(r) {
+		phys_addr_t start, end;
+		int rflags = flags;
+
+		if (memblock_is_nomap(r))
+			continue;
 		/*
-		 * for_each_mem_range may return sub-page-aligned boundaries
+		 * for_each_mem_region may return sub-page-aligned boundaries
 		 * after memblock_mark_nomap() splits regions at byte precision.
 		 * __create_pgd_mapping_locked aligns phys down to PAGE_MASK,
 		 * which could accidentally map no-map memory on the boundary.
@@ -1237,17 +1241,21 @@ static void __init map_mem(void)
 		 * regions. The cost is at most one page of unmapped gap at
 		 * each boundary.
 		 */
-		start = PAGE_ALIGN(start);
-		end = end & PAGE_MASK;
+		start = PAGE_ALIGN(r->base);
+		end = (r->base + r->size) & PAGE_MASK;
 		if (start >= end)
 			continue;
+
+		if (memblock_is_ptemap(r))
+			rflags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
+
 		/*
 		 * The linear map must allow allocation tags reading/writing
 		 * if MTE is present. Otherwise, it has the same attributes as
 		 * PAGE_KERNEL.
 		 */
 		__map_memblock(start, end, pgprot_tagged(PAGE_KERNEL),
-			       flags);
+			       rflags);
 	}
 }
 
-- 
2.56.0.542.g3ef89b7020-goog