target-mips: add KScratch registers

KScratch<n> Registers (CP0 Register 31, Selects 2 to 7)

The KScratch registers are read/write registers available for scratch pad
storage by kernel mode software. They are 32-bits in width for 32-bit
processors and 64-bits for 64-bit processors.

CP0Config4.KScrExist[2:7] bits indicate presence of CP0_KScratch1-6 registers.
For Release 6, all KScratch registers are required.

Signed-off-by: Leon Alrae <leon.alrae@imgtec.com>
Reviewed-by: Yongbok Kim <yongbok.kim@imgtec.com>

2 files changed, 47 insertions, 0 deletions

diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index 26e7894..91e781e 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -136,6 +136,7 @@ typedef struct mips_def_t mips_def_t;
 #define MIPS_TC_MAX 5
 #define MIPS_FPU_MAX 1
 #define MIPS_DSP_ACC 4
+#define MIPS_KSCRATCH_NUM 6
 
 typedef struct TCState TCState;
 struct TCState {
@@ -229,6 +230,7 @@ struct CPUMIPSState {
     target_ulong CP0_EntryLo0;
     target_ulong CP0_EntryLo1;
     target_ulong CP0_Context;
+    target_ulong CP0_KScratch[MIPS_KSCRATCH_NUM];
     int32_t CP0_PageMask;
     int32_t CP0_PageGrain;
     int32_t CP0_Wired;
@@ -375,6 +377,7 @@ struct CPUMIPSState {
     uint32_t CP0_Config4;
     uint32_t CP0_Config4_rw_bitmask;
 #define CP0C4_M    31
+#define CP0C4_KScrExist 16
     uint32_t CP0_Config5;
     uint32_t CP0_Config5_rw_bitmask;
 #define CP0C5_M          31
diff --git a/target-mips/translate.c b/target-mips/translate.c
index 446eb8a..167f9bc 100644
--- a/target-mips/translate.c
+++ b/target-mips/translate.c
@@ -1170,6 +1170,7 @@ typedef struct DisasContext {
     int bstate;
     target_ulong btarget;
     bool ulri;
+    int kscrexist;
 } DisasContext;
 
 enum {
@@ -4567,6 +4568,15 @@ static inline void gen_mtc0_store64 (TCGv arg, target_ulong off)
     tcg_gen_st_tl(arg, cpu_env, off);
 }
 
+static inline void gen_mfc0_unimplemented(DisasContext *ctx, TCGv arg)
+{
+    if (ctx->insn_flags & ISA_MIPS32R6) {
+        tcg_gen_movi_tl(arg, 0);
+    } else {
+        tcg_gen_movi_tl(arg, ~0);
+    }
+}
+
 static void gen_mfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
 {
     const char *rn = "invalid";
@@ -5149,6 +5159,16 @@ static void gen_mfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             gen_mfc0_load32(arg, offsetof(CPUMIPSState, CP0_DESAVE));
             rn = "DESAVE";
             break;
+        case 2 ... 7:
+            if (ctx->kscrexist & (1 << sel)) {
+                tcg_gen_ld_tl(arg, cpu_env,
+                              offsetof(CPUMIPSState, CP0_KScratch[sel-2]));
+                tcg_gen_ext32s_tl(arg, arg);
+                rn = "KScratch";
+            } else {
+                gen_mfc0_unimplemented(ctx, arg);
+            }
+            break;
         default:
             goto die;
         }
@@ -5757,6 +5777,13 @@ static void gen_mtc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             gen_mtc0_store32(arg, offsetof(CPUMIPSState, CP0_DESAVE));
             rn = "DESAVE";
             break;
+        case 2 ... 7:
+            if (ctx->kscrexist & (1 << sel)) {
+                tcg_gen_st_tl(arg, cpu_env,
+                              offsetof(CPUMIPSState, CP0_KScratch[sel-2]));
+                rn = "KScratch";
+            }
+            break;
         default:
             goto die;
         }
@@ -6344,6 +6371,15 @@ static void gen_dmfc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             gen_mfc0_load32(arg, offsetof(CPUMIPSState, CP0_DESAVE));
             rn = "DESAVE";
             break;
+        case 2 ... 7:
+            if (ctx->kscrexist & (1 << sel)) {
+                tcg_gen_ld_tl(arg, cpu_env,
+                              offsetof(CPUMIPSState, CP0_KScratch[sel-2]));
+                rn = "KScratch";
+            } else {
+                gen_mfc0_unimplemented(ctx, arg);
+            }
+            break;
         default:
             goto die;
         }
@@ -6943,6 +6979,13 @@ static void gen_dmtc0(DisasContext *ctx, TCGv arg, int reg, int sel)
             gen_mtc0_store32(arg, offsetof(CPUMIPSState, CP0_DESAVE));
             rn = "DESAVE";
             break;
+        case 2 ... 7:
+            if (ctx->kscrexist & (1 << sel)) {
+                tcg_gen_st_tl(arg, cpu_env,
+                              offsetof(CPUMIPSState, CP0_KScratch[sel-2]));
+                rn = "KScratch";
+            }
+            break;
         default:
             goto die;
         }
@@ -17414,6 +17457,7 @@ gen_intermediate_code_internal(MIPSCPU *cpu, TranslationBlock *tb,
     ctx.CP0_Config1 = env->CP0_Config1;
     ctx.tb = tb;
     ctx.bstate = BS_NONE;
+    ctx.kscrexist = (env->CP0_Config4 >> CP0C4_KScrExist) & 0xff;
     /* Restore delay slot state from the tb context.  */
     ctx.hflags = (uint32_t)tb->flags; /* FIXME: maybe use 64 bits here? */
     ctx.ulri = env->CP0_Config3 & (1 << CP0C3_ULRI);