[PATCH 2/2] riscv: Use PUD/PGDIR entries for linear mapping when possible

[Alexandre Ghiti]

Improve best_map_size so that PUD or PGDIR entries are used for linear
mapping when possible as it allows better TLB utilization.

Signed-off-by: Alexandre Ghiti <a...@ghiti.fr>
---
 arch/riscv/mm/init.c | 45 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 34 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 9a5c97e091c1..d275f9f834cf 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -424,13 +424,29 @@ static void __init create_pgd_mapping(pgd_t *pgdp,
        create_pgd_next_mapping(nextp, va, pa, sz, prot);
 }
 
-static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
+static bool is_map_size_ok(uintptr_t map_size, phys_addr_t base,
+                          uintptr_t base_virt, phys_addr_t size)
 {
-       /* Upgrade to PMD_SIZE mappings whenever possible */
-       if ((base & (PMD_SIZE - 1)) || (size & (PMD_SIZE - 1)))
-               return PAGE_SIZE;
+       return !((base & (map_size - 1)) || (base_virt & (map_size - 1)) ||
+                       (size < map_size));
+}
+
+static uintptr_t __init best_map_size(phys_addr_t base, uintptr_t base_virt,
+                                     phys_addr_t size)
+{
+#ifndef __PAGETABLE_PMD_FOLDED
+       if (is_map_size_ok(PGDIR_SIZE, base, base_virt, size))
+               return PGDIR_SIZE;
+
+       if (pgtable_l4_enabled)
+               if (is_map_size_ok(PUD_SIZE, base, base_virt, size))
+                       return PUD_SIZE;
+#endif
+
+       if (is_map_size_ok(PMD_SIZE, base, base_virt, size))
+               return PMD_SIZE;
 
-       return PMD_SIZE;
+       return PAGE_SIZE;
 }
 
 /*
@@ -576,7 +592,7 @@ void create_kernel_page_table(pgd_t *pgdir, uintptr_t 
map_size)
 asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 {
        uintptr_t va, end_va;
-       uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
+       uintptr_t map_size;
 
        load_pa = (uintptr_t)(&_start);
        load_sz = (uintptr_t)(&_end) - load_pa;
@@ -587,6 +603,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 
        kernel_virt_addr = KERNEL_VIRT_ADDR;
 
+       map_size = best_map_size(load_pa, PAGE_OFFSET, MAX_EARLY_MAPPING_SIZE);
        va_pa_offset = PAGE_OFFSET - load_pa;
        va_kernel_pa_offset = kernel_virt_addr - load_pa;
        pfn_base = PFN_DOWN(load_pa);
@@ -700,6 +717,8 @@ static void __init setup_vm_final(void)
 
        /* Map all memory banks */
        for_each_memblock(memory, reg) {
+               uintptr_t remaining_size;
+
                start = reg->base;
                end = start + reg->size;
 
@@ -707,15 +726,19 @@ static void __init setup_vm_final(void)
                        break;
                if (memblock_is_nomap(reg))
                        continue;
-               if (start <= __pa(PAGE_OFFSET) &&
-                   __pa(PAGE_OFFSET) < end)
-                       start = __pa(PAGE_OFFSET);
 
-               map_size = best_map_size(start, end - start);
-               for (pa = start; pa < end; pa += map_size) {
+               pa = start;
+               remaining_size = reg->size;
+
+               while (remaining_size) {
                        va = (uintptr_t)__va(pa);
+                       map_size = best_map_size(pa, va, remaining_size);
+
                        create_pgd_mapping(swapper_pg_dir, va, pa,
                                           map_size, PAGE_KERNEL);
+
+                       pa += map_size;
+                       remaining_size -= map_size;
                }
        }
 
-- 
2.20.1