[PATCHv3 1/5] arm64/mm: introduce pgtable allocator for idmap_pg_dir and init_pg_dir

[Pingfan Liu]

When building a pgtable, __create_pgd_mapping() resorts to pgtable
allocator to alloc mem.

By introducing an allocator, __create_pgd_mapping() can consider both
idmap_pg_dir and init_pg_dir as a memory pool, and get memory from them
during the building of pgtable.

Signed-off-by: Pingfan Liu <kernelfans at gmail.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Ard Biesheuvel <ardb at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Kristina Martsenko <kristina.martsenko at arm.com>
Cc: James Morse <james.morse at arm.com>
Cc: Steven Price <steven.price at arm.com>
Cc: Jonathan Cameron <Jonathan.Cameron at huawei.com>
Cc: Pavel Tatashin <pasha.tatashin at soleen.com>
Cc: Anshuman Khandual <anshuman.khandual at arm.com>
Cc: Atish Patra <atish.patra at wdc.com>
Cc: Mike Rapoport <rppt at kernel.org>
Cc: Logan Gunthorpe <logang at deltatee.com>
Cc: Mark Brown <broonie at kernel.org>
To: linux-arm-kernel at lists.infradead.org
---
 arch/arm64/mm/mmu.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 6dd9369e3ea0..f4fc905718ca 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -90,6 +90,28 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 }
 EXPORT_SYMBOL(phys_mem_access_prot);
 
+struct headpool {
+	phys_addr_t start;
+	unsigned long size;
+	unsigned long next_idx;
+};
+
+static struct headpool cur_pool __initdata;
+
+void __init set_cur_headpool(phys_addr_t start, unsigned long size)
+{
+	cur_pool.start = start;
+	cur_pool.size = size;
+	cur_pool.next_idx = 0;
+}
+
+phys_addr_t __init head_pgtable_alloc(unsigned long unused_a)
+{
+	unsigned long idx = cur_pool.next_idx++;
+
+	return cur_pool.start + (idx << PAGE_SHIFT);
+}
+
 static phys_addr_t __init early_pgtable_alloc(int shift)
 {
 	phys_addr_t phys;
-- 
2.29.2