target/riscv: Add support for Control Transfer Records extension CSRs.

This commit adds support for [m|s|vs]ctrcontrol, sctrstatus and
sctrdepth CSRs handling.

Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250205-b4-ctr_upstream_v6-v6-3-439d8e06c8ef@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.h

@@ -313,6 +313,11 @@ struct CPUArchState {
     target_ulong mcause;
     target_ulong mtval;  /* since: priv-1.10.0 */
 
+    uint64_t mctrctl;
+    uint32_t sctrdepth;
+    uint32_t sctrstatus;
+    uint64_t vsctrctl;
+
     /* Machine and Supervisor interrupt priorities */
     uint8_t miprio[64];
     uint8_t siprio[64];

target/riscv/cpu_cfg.h

@@ -133,6 +133,8 @@ struct RISCVCPUConfig {
     bool ext_zvfhmin;
     bool ext_smaia;
     bool ext_ssaia;
+    bool ext_smctr;
+    bool ext_ssctr;
     bool ext_sscofpmf;
     bool ext_smepmp;
     bool ext_smrnmi;

target/riscv/csr.c

@@ -635,6 +635,48 @@ static RISCVException hgatp(CPURISCVState *env, int csrno)
     return hmode(env, csrno);
 }
 
+/*
+ * M-mode:
+ * Without ext_smctr raise illegal inst excep.
+ * Otherwise everything is accessible to m-mode.
+ *
+ * S-mode:
+ * Without ext_ssctr or mstateen.ctr raise illegal inst excep.
+ * Otherwise everything other than mctrctl is accessible.
+ *
+ * VS-mode:
+ * Without ext_ssctr or mstateen.ctr raise illegal inst excep.
+ * Without hstateen.ctr raise virtual illegal inst excep.
+ * Otherwise allow sctrctl (vsctrctl), sctrstatus, 0x200-0x2ff entry range.
+ * Always raise illegal instruction exception for sctrdepth.
+ */
+static RISCVException ctr_mmode(CPURISCVState *env, int csrno)
+{
+    /* Check if smctr-ext is present */
+    if (riscv_cpu_cfg(env)->ext_smctr) {
+        return RISCV_EXCP_NONE;
+    }
+
+    return RISCV_EXCP_ILLEGAL_INST;
+}
+
+static RISCVException ctr_smode(CPURISCVState *env, int csrno)
+{
+    const RISCVCPUConfig *cfg = riscv_cpu_cfg(env);
+
+    if (!cfg->ext_smctr && !cfg->ext_ssctr) {
+        return RISCV_EXCP_ILLEGAL_INST;
+    }
+
+    RISCVException ret = smstateen_acc_ok(env, 0, SMSTATEEN0_CTR);
+    if (ret == RISCV_EXCP_NONE && csrno == CSR_SCTRDEPTH &&
+        env->virt_enabled) {
+        return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
+    }
+
+    return ret;
+}
+
 static RISCVException aia_hmode(CPURISCVState *env, int csrno)
 {
     int ret;
@@ -3216,6 +3258,10 @@ static RISCVException write_mstateen0(CPURISCVState *env, int csrno,
         wr_mask |= (SMSTATEEN0_AIA | SMSTATEEN0_IMSIC);
     }
 
+    if (riscv_cpu_cfg(env)->ext_ssctr) {
+        wr_mask |= SMSTATEEN0_CTR;
+    }
+
     return write_mstateen(env, csrno, wr_mask, new_val);
 }
 
@@ -3255,6 +3301,10 @@ static RISCVException write_mstateen0h(CPURISCVState *env, int csrno,
         wr_mask |= SMSTATEEN0_P1P13;
     }
 
+    if (riscv_cpu_cfg(env)->ext_ssctr) {
+        wr_mask |= SMSTATEEN0_CTR;
+    }
+
     return write_mstateenh(env, csrno, wr_mask, new_val);
 }
 
@@ -3309,6 +3359,10 @@ static RISCVException write_hstateen0(CPURISCVState *env, int csrno,
         wr_mask |= (SMSTATEEN0_AIA | SMSTATEEN0_IMSIC);
     }
 
+    if (riscv_cpu_cfg(env)->ext_ssctr) {
+        wr_mask |= SMSTATEEN0_CTR;
+    }
+
     return write_hstateen(env, csrno, wr_mask, new_val);
 }
 
@@ -3348,6 +3402,10 @@ static RISCVException write_hstateen0h(CPURISCVState *env, int csrno,
 {
     uint64_t wr_mask = SMSTATEEN_STATEEN | SMSTATEEN0_HSENVCFG;
 
+    if (riscv_cpu_cfg(env)->ext_ssctr) {
+        wr_mask |= SMSTATEEN0_CTR;
+    }
+
     return write_hstateenh(env, csrno, wr_mask, new_val);
 }
 
@@ -4068,6 +4126,86 @@ static RISCVException write_satp(CPURISCVState *env, int csrno,
     return RISCV_EXCP_NONE;
 }
 
+static RISCVException rmw_sctrdepth(CPURISCVState *env, int csrno,
+                                    target_ulong *ret_val,
+                                    target_ulong new_val, target_ulong wr_mask)
+{
+    uint64_t mask = wr_mask & SCTRDEPTH_MASK;
+
+    if (ret_val) {
+        *ret_val = env->sctrdepth;
+    }
+
+    env->sctrdepth = (env->sctrdepth & ~mask) | (new_val & mask);
+
+    /* Correct depth. */
+    if (mask) {
+        uint64_t depth = get_field(env->sctrdepth, SCTRDEPTH_MASK);
+
+        if (depth > SCTRDEPTH_MAX) {
+            depth = SCTRDEPTH_MAX;
+            env->sctrdepth = set_field(env->sctrdepth, SCTRDEPTH_MASK, depth);
+        }
+
+        /* Update sctrstatus.WRPTR with a legal value */
+        depth = 16 << depth;
+        env->sctrstatus =
+            env->sctrstatus & (~SCTRSTATUS_WRPTR_MASK | (depth - 1));
+    }
+
+    return RISCV_EXCP_NONE;
+}
+
+static RISCVException rmw_sctrstatus(CPURISCVState *env, int csrno,
+                                     target_ulong *ret_val,
+                                     target_ulong new_val, target_ulong wr_mask)
+{
+    uint32_t depth = 16 << get_field(env->sctrdepth, SCTRDEPTH_MASK);
+    uint32_t mask = wr_mask & SCTRSTATUS_MASK;
+
+    if (ret_val) {
+        *ret_val = env->sctrstatus;
+    }
+
+    env->sctrstatus = (env->sctrstatus & ~mask) | (new_val & mask);
+
+    /* Update sctrstatus.WRPTR with a legal value */
+    env->sctrstatus = env->sctrstatus & (~SCTRSTATUS_WRPTR_MASK | (depth - 1));
+
+    return RISCV_EXCP_NONE;
+}
+
+static RISCVException rmw_xctrctl(CPURISCVState *env, int csrno,
+                                    target_ulong *ret_val,
+                                    target_ulong new_val, target_ulong wr_mask)
+{
+    uint64_t csr_mask, mask = wr_mask;
+    uint64_t *ctl_ptr = &env->mctrctl;
+
+    if (csrno == CSR_MCTRCTL) {
+        csr_mask = MCTRCTL_MASK;
+    } else if (csrno == CSR_SCTRCTL && !env->virt_enabled) {
+        csr_mask = SCTRCTL_MASK;
+    } else {
+        /*
+         * This is for csrno == CSR_SCTRCTL and env->virt_enabled == true
+         * or csrno == CSR_VSCTRCTL.
+         */
+        csr_mask = VSCTRCTL_MASK;
+        ctl_ptr = &env->vsctrctl;
+    }
+
+    mask &= csr_mask;
+
+    if (ret_val) {
+        *ret_val = *ctl_ptr & csr_mask;
+    }
+
+    *ctl_ptr = (*ctl_ptr & ~mask) | (new_val & mask);
+
+    return RISCV_EXCP_NONE;
+}
+
 static RISCVException read_vstopi(CPURISCVState *env, int csrno,
                                   target_ulong *val)
 {
@@ -5821,6 +5959,12 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     [CSR_TINFO]     =  { "tinfo",    debug, read_tinfo,    write_ignore   },
     [CSR_MCONTEXT]  =  { "mcontext", debug, read_mcontext, write_mcontext },
 
+    [CSR_MCTRCTL]    = { "mctrctl",    ctr_mmode,  NULL, NULL, rmw_xctrctl    },
+    [CSR_SCTRCTL]    = { "sctrctl",    ctr_smode,  NULL, NULL, rmw_xctrctl    },
+    [CSR_VSCTRCTL]   = { "vsctrctl",   ctr_smode,  NULL, NULL, rmw_xctrctl    },
+    [CSR_SCTRDEPTH]  = { "sctrdepth",  ctr_smode,  NULL, NULL, rmw_sctrdepth  },
+    [CSR_SCTRSTATUS] = { "sctrstatus", ctr_smode,  NULL, NULL, rmw_sctrstatus },
+
     /* Performance Counters */
     [CSR_HPMCOUNTER3]    = { "hpmcounter3",    ctr,    read_hpmcounter },
     [CSR_HPMCOUNTER4]    = { "hpmcounter4",    ctr,    read_hpmcounter },