target/riscv: Split misa.mxl and misa.ext

The hw representation of misa.mxl is at the high bits of the
misa csr.  Representing this in the same way inside QEMU
results in overly complex code trying to check that field.

Reviewed-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20211020031709.359469-4-richard.henderson@linaro.org
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

linux-user/elfload.c

@@ -1448,7 +1448,7 @@ static uint32_t get_elf_hwcap(void)
     uint32_t mask = MISA_BIT('I') | MISA_BIT('M') | MISA_BIT('A')
                     | MISA_BIT('F') | MISA_BIT('D') | MISA_BIT('C');
 
-    return cpu->env.misa & mask;
+    return cpu->env.misa_ext & mask;
 #undef MISA_BIT
 }
 

linux-user/riscv/cpu_loop.c

@@ -133,7 +133,7 @@ void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs)
     env->gpr[xSP] = regs->sp;
     env->elf_flags = info->elf_flags;
 
-    if ((env->misa & RVE) && !(env->elf_flags & EF_RISCV_RVE)) {
+    if ((env->misa_ext & RVE) && !(env->elf_flags & EF_RISCV_RVE)) {
         error_report("Incompatible ELF: RVE cpu requires RVE ABI binary");
         exit(EXIT_FAILURE);
     }

target/riscv/cpu.c

@@ -110,16 +110,13 @@ const char *riscv_cpu_get_trap_name(target_ulong cause, bool async)
 
 bool riscv_cpu_is_32bit(CPURISCVState *env)
 {
-    if (env->misa & RV64) {
-        return false;
-    }
-
-    return true;
+    return env->misa_mxl == MXL_RV32;
 }
 
-static void set_misa(CPURISCVState *env, target_ulong misa)
+static void set_misa(CPURISCVState *env, RISCVMXL mxl, uint32_t ext)
 {
-    env->misa_mask = env->misa = misa;
+    env->misa_mxl_max = env->misa_mxl = mxl;
+    env->misa_ext_mask = env->misa_ext = ext;
 }
 
 static void set_priv_version(CPURISCVState *env, int priv_ver)
@@ -148,9 +145,9 @@ static void riscv_any_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
 #if defined(TARGET_RISCV32)
-    set_misa(env, RV32 | RVI | RVM | RVA | RVF | RVD | RVC | RVU);
+    set_misa(env, MXL_RV32, RVI | RVM | RVA | RVF | RVD | RVC | RVU);
 #elif defined(TARGET_RISCV64)
-    set_misa(env, RV64 | RVI | RVM | RVA | RVF | RVD | RVC | RVU);
+    set_misa(env, MXL_RV64, RVI | RVM | RVA | RVF | RVD | RVC | RVU);
 #endif
     set_priv_version(env, PRIV_VERSION_1_11_0);
 }
@@ -160,20 +157,20 @@ static void rv64_base_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
     /* We set this in the realise function */
-    set_misa(env, RV64);
+    set_misa(env, MXL_RV64, 0);
 }
 
 static void rv64_sifive_u_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
-    set_misa(env, RV64 | RVI | RVM | RVA | RVF | RVD | RVC | RVS | RVU);
+    set_misa(env, MXL_RV64, RVI | RVM | RVA | RVF | RVD | RVC | RVS | RVU);
     set_priv_version(env, PRIV_VERSION_1_10_0);
 }
 
 static void rv64_sifive_e_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
-    set_misa(env, RV64 | RVI | RVM | RVA | RVC | RVU);
+    set_misa(env, MXL_RV64, RVI | RVM | RVA | RVC | RVU);
     set_priv_version(env, PRIV_VERSION_1_10_0);
     qdev_prop_set_bit(DEVICE(obj), "mmu", false);
 }
@@ -182,20 +179,20 @@ static void rv32_base_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
     /* We set this in the realise function */
-    set_misa(env, RV32);
+    set_misa(env, MXL_RV32, 0);
 }
 
 static void rv32_sifive_u_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
-    set_misa(env, RV32 | RVI | RVM | RVA | RVF | RVD | RVC | RVS | RVU);
+    set_misa(env, MXL_RV32, RVI | RVM | RVA | RVF | RVD | RVC | RVS | RVU);
     set_priv_version(env, PRIV_VERSION_1_10_0);
 }
 
 static void rv32_sifive_e_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
-    set_misa(env, RV32 | RVI | RVM | RVA | RVC | RVU);
+    set_misa(env, MXL_RV32, RVI | RVM | RVA | RVC | RVU);
     set_priv_version(env, PRIV_VERSION_1_10_0);
     qdev_prop_set_bit(DEVICE(obj), "mmu", false);
 }
@@ -203,7 +200,7 @@ static void rv32_sifive_e_cpu_init(Object *obj)
 static void rv32_ibex_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
-    set_misa(env, RV32 | RVI | RVM | RVC | RVU);
+    set_misa(env, MXL_RV32, RVI | RVM | RVC | RVU);
     set_priv_version(env, PRIV_VERSION_1_10_0);
     qdev_prop_set_bit(DEVICE(obj), "mmu", false);
     qdev_prop_set_bit(DEVICE(obj), "x-epmp", true);
@@ -212,7 +209,7 @@ static void rv32_ibex_cpu_init(Object *obj)
 static void rv32_imafcu_nommu_cpu_init(Object *obj)
 {
     CPURISCVState *env = &RISCV_CPU(obj)->env;
-    set_misa(env, RV32 | RVI | RVM | RVA | RVF | RVC | RVU);
+    set_misa(env, MXL_RV32, RVI | RVM | RVA | RVF | RVC | RVU);
     set_priv_version(env, PRIV_VERSION_1_10_0);
     set_resetvec(env, DEFAULT_RSTVEC);
     qdev_prop_set_bit(DEVICE(obj), "mmu", false);
@@ -360,6 +357,7 @@ static void riscv_cpu_reset(DeviceState *dev)
 
     mcc->parent_reset(dev);
 #ifndef CONFIG_USER_ONLY
+    env->misa_mxl = env->misa_mxl_max;
     env->priv = PRV_M;
     env->mstatus &= ~(MSTATUS_MIE | MSTATUS_MPRV);
     env->mcause = 0;
@@ -388,7 +386,6 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
     CPURISCVState *env = &cpu->env;
     RISCVCPUClass *mcc = RISCV_CPU_GET_CLASS(dev);
     int priv_version = 0;
-    target_ulong target_misa = env->misa;
     Error *local_err = NULL;
 
     cpu_exec_realizefn(cs, &local_err);
@@ -434,8 +431,23 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
 
     set_resetvec(env, cpu->cfg.resetvec);
 
-    /* If only XLEN is set for misa, then set misa from properties */
-    if (env->misa == RV32 || env->misa == RV64) {
+    /* Validate that MISA_MXL is set properly. */
+    switch (env->misa_mxl_max) {
+#ifdef TARGET_RISCV64
+    case MXL_RV64:
+        break;
+#endif
+    case MXL_RV32:
+        break;
+    default:
+        g_assert_not_reached();
+    }
+    assert(env->misa_mxl_max == env->misa_mxl);
+
+    /* If only MISA_EXT is unset for misa, then set it from properties */
+    if (env->misa_ext == 0) {
+        uint32_t ext = 0;
+
         /* Do some ISA extension error checking */
         if (cpu->cfg.ext_i && cpu->cfg.ext_e) {
             error_setg(errp,
@@ -462,38 +474,38 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
 
         /* Set the ISA extensions, checks should have happened above */
         if (cpu->cfg.ext_i) {
-            target_misa |= RVI;
+            ext |= RVI;
         }
         if (cpu->cfg.ext_e) {
-            target_misa |= RVE;
+            ext |= RVE;
         }
         if (cpu->cfg.ext_m) {
-            target_misa |= RVM;
+            ext |= RVM;
         }
         if (cpu->cfg.ext_a) {
-            target_misa |= RVA;
+            ext |= RVA;
         }
         if (cpu->cfg.ext_f) {
-            target_misa |= RVF;
+            ext |= RVF;
         }
         if (cpu->cfg.ext_d) {
-            target_misa |= RVD;
+            ext |= RVD;
         }
         if (cpu->cfg.ext_c) {
-            target_misa |= RVC;
+            ext |= RVC;
         }
         if (cpu->cfg.ext_s) {
-            target_misa |= RVS;
+            ext |= RVS;
         }
         if (cpu->cfg.ext_u) {
-            target_misa |= RVU;
+            ext |= RVU;
         }
         if (cpu->cfg.ext_h) {
-            target_misa |= RVH;
+            ext |= RVH;
         }
         if (cpu->cfg.ext_v) {
             int vext_version = VEXT_VERSION_0_07_1;
-            target_misa |= RVV;
+            ext |= RVV;
             if (!is_power_of_2(cpu->cfg.vlen)) {
                 error_setg(errp,
                         "Vector extension VLEN must be power of 2");
@@ -532,7 +544,7 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
             set_vext_version(env, vext_version);
         }
 
-        set_misa(env, target_misa);
+        set_misa(env, env->misa_mxl, ext);
     }
 
     riscv_cpu_register_gdb_regs_for_features(cs);
@@ -708,7 +720,7 @@ char *riscv_isa_string(RISCVCPU *cpu)
     char *isa_str = g_new(char, maxlen);
     char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", TARGET_LONG_BITS);
     for (i = 0; i < sizeof(riscv_exts); i++) {
-        if (cpu->env.misa & RV(riscv_exts[i])) {
+        if (cpu->env.misa_ext & RV(riscv_exts[i])) {
             *p++ = qemu_tolower(riscv_exts[i]);
         }
     }

target/riscv/cpu.h

@@ -25,6 +25,7 @@
 #include "exec/cpu-defs.h"
 #include "fpu/softfloat-types.h"
 #include "qom/object.h"
+#include "cpu_bits.h"
 
 #define TCG_GUEST_DEFAULT_MO 0
 
@@ -51,9 +52,6 @@
 # define TYPE_RISCV_CPU_BASE            TYPE_RISCV_CPU_BASE64
 #endif
 
-#define RV32 ((target_ulong)1 << (TARGET_LONG_BITS - 2))
-#define RV64 ((target_ulong)2 << (TARGET_LONG_BITS - 2))
-
 #define RV(x) ((target_ulong)1 << (x - 'A'))
 
 #define RVI RV('I')
@@ -133,8 +131,12 @@ struct CPURISCVState {
     target_ulong priv_ver;
     target_ulong bext_ver;
     target_ulong vext_ver;
-    target_ulong misa;
-    target_ulong misa_mask;
+
+    /* RISCVMXL, but uint32_t for vmstate migration */
+    uint32_t misa_mxl;      /* current mxl */
+    uint32_t misa_mxl_max;  /* max mxl for this cpu */
+    uint32_t misa_ext;      /* current extensions */
+    uint32_t misa_ext_mask; /* max ext for this cpu */
 
     uint32_t features;
 
@@ -313,7 +315,7 @@ struct RISCVCPU {
 
 static inline int riscv_has_ext(CPURISCVState *env, target_ulong ext)
 {
-    return (env->misa & ext) != 0;
+    return (env->misa_ext & ext) != 0;
 }
 
 static inline bool riscv_feature(CPURISCVState *env, int feature)
@@ -322,7 +324,6 @@ static inline bool riscv_feature(CPURISCVState *env, int feature)
 }
 
 #include "cpu_user.h"
-#include "cpu_bits.h"
 
 extern const char * const riscv_int_regnames[];
 extern const char * const riscv_fpr_regnames[];

target/riscv/csr.c

@@ -39,7 +39,7 @@ static RISCVException fs(CPURISCVState *env, int csrno)
 {
 #if !defined(CONFIG_USER_ONLY)
     /* loose check condition for fcsr in vector extension */
-    if ((csrno == CSR_FCSR) && (env->misa & RVV)) {
+    if ((csrno == CSR_FCSR) && (env->misa_ext & RVV)) {
         return RISCV_EXCP_NONE;
     }
     if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
@@ -51,7 +51,7 @@ static RISCVException fs(CPURISCVState *env, int csrno)
 
 static RISCVException vs(CPURISCVState *env, int csrno)
 {
-    if (env->misa & RVV) {
+    if (env->misa_ext & RVV) {
         return RISCV_EXCP_NONE;
     }
     return RISCV_EXCP_ILLEGAL_INST;
@@ -557,7 +557,22 @@ static RISCVException write_mstatush(CPURISCVState *env, int csrno,
 static RISCVException read_misa(CPURISCVState *env, int csrno,
                                 target_ulong *val)
 {
-    *val = env->misa;
+    target_ulong misa;
+
+    switch (env->misa_mxl) {
+    case MXL_RV32:
+        misa = (target_ulong)MXL_RV32 << 30;
+        break;
+#ifdef TARGET_RISCV64
+    case MXL_RV64:
+        misa = (target_ulong)MXL_RV64 << 62;
+        break;
+#endif
+    default:
+        g_assert_not_reached();
+    }
+
+    *val = misa | env->misa_ext;
     return RISCV_EXCP_NONE;
 }
 
@@ -583,8 +598,13 @@ static RISCVException write_misa(CPURISCVState *env, int csrno,
         return RISCV_EXCP_NONE;
     }
 
+    /*
+     * misa.MXL writes are not supported by QEMU.
+     * Drop writes to those bits.
+     */
+
     /* Mask extensions that are not supported by this hart */
-    val &= env->misa_mask;
+    val &= env->misa_ext_mask;
 
     /* Mask extensions that are not supported by QEMU */
     val &= (RVI | RVE | RVM | RVA | RVF | RVD | RVC | RVS | RVU);
@@ -601,20 +621,14 @@ static RISCVException write_misa(CPURISCVState *env, int csrno,
         val &= ~RVC;
     }
 
-    /* misa.MXL writes are not supported by QEMU */
-    if (riscv_cpu_is_32bit(env)) {
-        val = (env->misa & MISA32_MXL) | (val & ~MISA32_MXL);
-    } else {
-        val = (env->misa & MISA64_MXL) | (val & ~MISA64_MXL);
+    /* If nothing changed, do nothing. */
+    if (val == env->misa_ext) {
+        return RISCV_EXCP_NONE;
     }
 
     /* flush translation cache */
-    if (val != env->misa) {
-        tb_flush(env_cpu(env));
-    }
-
-    env->misa = val;
-
+    tb_flush(env_cpu(env));
+    env->misa_ext = val;
     return RISCV_EXCP_NONE;
 }
 

target/riscv/gdbstub.c

@@ -54,10 +54,10 @@ int riscv_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
 static int riscv_gdb_get_fpu(CPURISCVState *env, GByteArray *buf, int n)
 {
     if (n < 32) {
-        if (env->misa & RVD) {
+        if (env->misa_ext & RVD) {
             return gdb_get_reg64(buf, env->fpr[n]);
         }
-        if (env->misa & RVF) {
+        if (env->misa_ext & RVF) {
             return gdb_get_reg32(buf, env->fpr[n]);
         }
     /* there is hole between ft11 and fflags in fpu.xml */
@@ -191,10 +191,10 @@ void riscv_cpu_register_gdb_regs_for_features(CPUState *cs)
 {
     RISCVCPU *cpu = RISCV_CPU(cs);
     CPURISCVState *env = &cpu->env;
-    if (env->misa & RVD) {
+    if (env->misa_ext & RVD) {
         gdb_register_coprocessor(cs, riscv_gdb_get_fpu, riscv_gdb_set_fpu,
                                  36, "riscv-64bit-fpu.xml", 0);
-    } else if (env->misa & RVF) {
+    } else if (env->misa_ext & RVF) {
         gdb_register_coprocessor(cs, riscv_gdb_get_fpu, riscv_gdb_set_fpu,
                                  36, "riscv-32bit-fpu.xml", 0);
     }

target/riscv/machine.c

@@ -140,8 +140,8 @@ static const VMStateDescription vmstate_hyper = {
 
 const VMStateDescription vmstate_riscv_cpu = {
     .name = "cpu",
-    .version_id = 2,
-    .minimum_version_id = 2,
+    .version_id = 3,
+    .minimum_version_id = 3,
     .fields = (VMStateField[]) {
         VMSTATE_UINTTL_ARRAY(env.gpr, RISCVCPU, 32),
         VMSTATE_UINT64_ARRAY(env.fpr, RISCVCPU, 32),
@@ -153,8 +153,10 @@ const VMStateDescription vmstate_riscv_cpu = {
         VMSTATE_UINTTL(env.guest_phys_fault_addr, RISCVCPU),
         VMSTATE_UINTTL(env.priv_ver, RISCVCPU),
         VMSTATE_UINTTL(env.vext_ver, RISCVCPU),
-        VMSTATE_UINTTL(env.misa, RISCVCPU),
-        VMSTATE_UINTTL(env.misa_mask, RISCVCPU),
+        VMSTATE_UINT32(env.misa_mxl, RISCVCPU),
+        VMSTATE_UINT32(env.misa_ext, RISCVCPU),
+        VMSTATE_UINT32(env.misa_mxl_max, RISCVCPU),
+        VMSTATE_UINT32(env.misa_ext_mask, RISCVCPU),
         VMSTATE_UINT32(env.features, RISCVCPU),
         VMSTATE_UINTTL(env.priv, RISCVCPU),
         VMSTATE_UINTTL(env.virt, RISCVCPU),

target/riscv/translate.c

@@ -55,7 +55,8 @@ typedef struct DisasContext {
     /* pc_succ_insn points to the instruction following base.pc_next */
     target_ulong pc_succ_insn;
     target_ulong priv_ver;
-    target_ulong misa;
+    RISCVMXL xl;
+    uint32_t misa_ext;
     uint32_t opcode;
     uint32_t mstatus_fs;
     uint32_t mstatus_hs_fs;
@@ -86,7 +87,7 @@ typedef struct DisasContext {
 
 static inline bool has_ext(DisasContext *ctx, uint32_t ext)
 {
-    return ctx->misa & ext;
+    return ctx->misa_ext & ext;
 }
 
 #ifdef TARGET_RISCV32
@@ -96,7 +97,7 @@ static inline bool has_ext(DisasContext *ctx, uint32_t ext)
 #else
 static inline bool is_32bit(DisasContext *ctx)
 {
-    return (ctx->misa & RV32) == RV32;
+    return ctx->xl == MXL_RV32;
 }
 #endif
 
@@ -513,7 +514,8 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
 #else
     ctx->virt_enabled = false;
 #endif
-    ctx->misa = env->misa;
+    ctx->xl = env->misa_mxl;
+    ctx->misa_ext = env->misa_ext;
     ctx->frm = -1;  /* unknown rounding mode */
     ctx->ext_ifencei = cpu->cfg.ext_ifencei;
     ctx->vlen = cpu->cfg.vlen;