target/mips: Add CP0 PWBase register

Add PWBase register (CP0 Register 5, Select 5).

The PWBase register contains the Page Table Base virtual address.

This register is required for the hardware page walker feature. It
exists only if Config3 PW bit is set to 1.

Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: Yongbok Kim <yongbok.kim@mips.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>

target/mips/cpu.h

@@ -416,6 +416,7 @@ struct CPUMIPSState {
 #define CP0SC2_XR       56
 #define CP0SC2_XR_MASK  (0xFFULL << CP0SC2_XR)
 #define CP0SC2_MASK     (CP0SC_1GMASK | (CP0SC_1GMASK << 16) | CP0SC2_XR_MASK)
+    target_ulong CP0_PWBase;
 /*
  * CP0 Register 6
  */

target/mips/machine.c

@@ -212,8 +212,8 @@ const VMStateDescription vmstate_tlb = {
 
 const VMStateDescription vmstate_mips_cpu = {
     .name = "cpu",
-    .version_id = 11,
+    .version_id = 12,
-    .minimum_version_id = 11,
+    .minimum_version_id = 12,
     .post_load = cpu_post_load,
     .fields = (VMStateField[]) {
         /* Active TC */
@@ -256,6 +256,7 @@ const VMStateDescription vmstate_mips_cpu = {
         VMSTATE_UINTTL(env.CP0_SegCtl0, MIPSCPU),
         VMSTATE_UINTTL(env.CP0_SegCtl1, MIPSCPU),
         VMSTATE_UINTTL(env.CP0_SegCtl2, MIPSCPU),
+        VMSTATE_UINTTL(env.CP0_PWBase, MIPSCPU),
         VMSTATE_INT32(env.CP0_Wired, MIPSCPU),
         VMSTATE_INT32(env.CP0_SRSConf0, MIPSCPU),
         VMSTATE_INT32(env.CP0_SRSConf1, MIPSCPU),

target/mips/translate.c

@@ -2478,6 +2478,19 @@ static inline void check_xnp(DisasContext *ctx)
     }
 }
 
+#ifndef CONFIG_USER_ONLY
+/*
+ * This code generates a "reserved instruction" exception if the
+ * Config3 PW bit is NOT set.
+ */
+static inline void check_pw(DisasContext *ctx)
+{
+    if (unlikely(!(ctx->CP0_Config3 & (1 << CP0C3_PW)))) {
+        generate_exception_end(ctx, EXCP_RI);
+    }
+}
+#endif
+
 /*
  * This code generates a "reserved instruction" exception if the
  * Config3 MT bit is NOT set.
@@ -6088,6 +6101,11 @@ static void gen_mfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             tcg_gen_ext32s_tl(arg, arg);
             rn = "SegCtl2";
             break;
+        case 5:
+            check_pw(ctx);
+            gen_mfc0_load32(arg, offsetof(CPUMIPSState, CP0_PWBase));
+            rn = "PWBase";
+            break;
         default:
             goto cp0_unimplemented;
         }
@@ -6789,6 +6807,11 @@ static void gen_mtc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             gen_helper_mtc0_segctl2(cpu_env, arg);
             rn = "SegCtl2";
             break;
+        case 5:
+            check_pw(ctx);
+            gen_mtc0_store32(arg, offsetof(CPUMIPSState, CP0_PWBase));
+            rn = "PWBase";
+            break;
         default:
             goto cp0_unimplemented;
         }
@@ -7499,6 +7522,11 @@ static void gen_dmfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             tcg_gen_ld_tl(arg, cpu_env, offsetof(CPUMIPSState, CP0_SegCtl2));
             rn = "SegCtl2";
             break;
+        case 5:
+            check_pw(ctx);
+            tcg_gen_ld_tl(arg, cpu_env, offsetof(CPUMIPSState, CP0_PWBase));
+            rn = "PWBase";
+            break;
         default:
             goto cp0_unimplemented;
         }
@@ -8182,6 +8210,11 @@ static void gen_dmtc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             gen_helper_mtc0_segctl2(cpu_env, arg);
             rn = "SegCtl2";
             break;
+        case 5:
+            check_pw(ctx);
+            tcg_gen_st_tl(arg, cpu_env, offsetof(CPUMIPSState, CP0_PWBase));
+            rn = "PWBase";
+            break;
         default:
             goto cp0_unimplemented;
         }