target/riscv: add support for svnapot extension

- add PTE_N bit
- add PTE_N bit check for inner PTE
- update address translation to support 64KiB continuous region (napot_bits = 4)

Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220204022658.18097-4-liweiwei@iscas.ac.cn>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -774,6 +774,8 @@ static Property riscv_cpu_properties[] = {
     DEFINE_PROP_UINT16("vlen", RISCVCPU, cfg.vlen, 128),
     DEFINE_PROP_UINT16("elen", RISCVCPU, cfg.elen, 64),
 
+    DEFINE_PROP_BOOL("svnapot", RISCVCPU, cfg.ext_svnapot, false),
+
     DEFINE_PROP_BOOL("zba", RISCVCPU, cfg.ext_zba, true),
     DEFINE_PROP_BOOL("zbb", RISCVCPU, cfg.ext_zbb, true),
     DEFINE_PROP_BOOL("zbc", RISCVCPU, cfg.ext_zbc, true),

target/riscv/cpu_bits.h

@@ -561,6 +561,7 @@ typedef enum {
 #define PTE_A               0x040 /* Accessed */
 #define PTE_D               0x080 /* Dirty */
 #define PTE_SOFT            0x300 /* Reserved for Software */
+#define PTE_N               0x8000000000000000ULL /* NAPOT translation */
 
 /* Page table PPN shift amount */
 #define PTE_PPN_SHIFT       10

target/riscv/cpu_helper.c

@@ -753,6 +753,8 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
     bool use_background = false;
     hwaddr ppn;
     RISCVCPU *cpu = env_archcpu(env);
+    int napot_bits = 0;
+    target_ulong napot_mask;
 
     /*
      * Check if we should use the background registers for the two
@@ -937,7 +939,7 @@ restart:
             return TRANSLATE_FAIL;
         } else if (!(pte & (PTE_R | PTE_W | PTE_X))) {
             /* Inner PTE, continue walking */
-            if (pte & (PTE_D | PTE_A | PTE_U)) {
+            if (pte & (PTE_D | PTE_A | PTE_U | PTE_N)) {
                 return TRANSLATE_FAIL;
             }
             base = ppn << PGSHIFT;
@@ -1013,8 +1015,18 @@ restart:
             /* for superpage mappings, make a fake leaf PTE for the TLB's
                benefit. */
             target_ulong vpn = addr >> PGSHIFT;
-            *physical = ((ppn | (vpn & ((1L << ptshift) - 1))) << PGSHIFT) |
-                        (addr & ~TARGET_PAGE_MASK);
+
+            if (cpu->cfg.ext_svnapot && (pte & PTE_N)) {
+                napot_bits = ctzl(ppn) + 1;
+                if ((i != (levels - 1)) || (napot_bits != 4)) {
+                    return TRANSLATE_FAIL;
+                }
+            }
+
+            napot_mask = (1 << napot_bits) - 1;
+            *physical = (((ppn & ~napot_mask) | (vpn & napot_mask) |
+                          (vpn & (((target_ulong)1 << ptshift) - 1))
+                         ) << PGSHIFT) | (addr & ~TARGET_PAGE_MASK);
 
             /* set permissions on the TLB entry */
             if ((pte & PTE_R) || ((pte & PTE_X) && mxr)) {