arm64: mm: Create gigabyte kernel logical mappings where possible

We have the capability to map 1GB level 1 blocks when using a 4K
granule.

This patch adjusts the create_mapping logic s.t. when mapping physical
memory on boot, we attempt to use a 1GB block if both the VA and PA
start and end are 1GB aligned. This both reduces the levels of lookup
required to resolve a kernel logical address, as well as reduces TLB
pressure on cores that support 1GB TLB entries.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
Tested-by: Jungseok Lee <jays.lee@samsung.com>
[catalin.marinas@arm.com: s/prot_sect_kernel/PROT_SECT_NORMAL_EXEC/]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 27 insertions, 1 deletions

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2c0e1dda8163..3a729de96f15 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -195,7 +195,30 @@ static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
 
 	do {
 		next = pud_addr_end(addr, end);
-		alloc_init_pmd(pud, addr, next, phys);
+
+		/*
+		 * For 4K granule only, attempt to put down a 1GB block
+		 */
+		if ((PAGE_SHIFT == 12) &&
+		    ((addr | next | phys) & ~PUD_MASK) == 0) {
+			pud_t old_pud = *pud;
+			set_pud(pud, __pud(phys | PROT_SECT_NORMAL_EXEC));
+
+			/*
+			 * If we have an old value for a pud, it will
+			 * be pointing to a pmd table that we no longer
+			 * need (from swapper_pg_dir).
+			 *
+			 * Look up the old pmd table and free it.
+			 */
+			if (!pud_none(old_pud)) {
+				phys_addr_t table = __pa(pmd_offset(&old_pud, 0));
+				memblock_free(table, PAGE_SIZE);
+				flush_tlb_all();
+			}
+		} else {
+			alloc_init_pmd(pud, addr, next, phys);
+		}
 		phys += next - addr;
 	} while (pud++, addr = next, addr != end);
 }
@@ -338,6 +361,9 @@ int kern_addr_valid(unsigned long addr)
 	if (pud_none(*pud))
 		return 0;
 
+	if (pud_sect(*pud))
+		return pfn_valid(pud_pfn(*pud));
+
 	pmd = pmd_offset(pud, addr);
 	if (pmd_none(*pmd))
 		return 0;