[PATCH v4 2/4] target/riscv: add support for svnapot extension

[Weiwei Li <liweiwei@iscas.ac.cn>]

- 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>
---
 target/riscv/cpu.c        |  2 ++
 target/riscv/cpu.h        |  1 +
 target/riscv/cpu_bits.h   |  1 +
 target/riscv/cpu_helper.c | 22 +++++++++++++++++-----
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 9bc25d3055..ff6c86c85b 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -668,6 +668,8 @@ 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),
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 4d63086765..d3d17cde82 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -327,6 +327,7 @@ struct RISCVCPU {
         bool ext_counters;
         bool ext_ifencei;
         bool ext_icsr;
+        bool ext_svnapot;
         bool ext_zfh;
         bool ext_zfhmin;
 
diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index 5a6d49aa64..bc23e3b523 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -486,6 +486,7 @@ typedef enum {
 #define PTE_A               0x040 /* Accessed */
 #define PTE_D               0x080 /* Dirty */
 #define PTE_SOFT            0x300 /* Reserved for Software */
+#define PTE_N               0x8000000000000000 /* NAPOT translation */
 
 /* Page table PPN shift amount */
 #define PTE_PPN_SHIFT       10
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index d84cde424d..832a2dd79c 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -619,14 +619,17 @@ restart:
             return TRANSLATE_FAIL;
         }
 
-        hwaddr ppn = pte >> PTE_PPN_SHIFT;
+        hwaddr ppn = (pte & ~(target_ulong)PTE_N) >> PTE_PPN_SHIFT;
 
-        if (!(pte & PTE_V)) {
+        RISCVCPU *cpu = env_archcpu(env);
+        if (!cpu->cfg.ext_svnapot && (pte & PTE_N)) {
+            return TRANSLATE_FAIL;
+        } else if (!(pte & PTE_V)) {
             /* Invalid PTE */
             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;
@@ -702,8 +705,17 @@ 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);
+
+            int napot_bits = ((pte & PTE_N) ? (ctzl(ppn) + 1) : 0);
+            if (((pte & PTE_N) && ((ppn == 0) || (i != (levels - 1)))) ||
+                (napot_bits != 0 && napot_bits != 4)) {
+                return TRANSLATE_FAIL;
+            }
+
+            *physical = (((ppn & ~(((target_ulong)1 << napot_bits) - 1)) |
+                          (vpn & (((target_ulong)1 << napot_bits) - 1)) |
+                          (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)) {
-- 
2.17.1