target/riscv: Add CTR sctrclr instruction.

CTR extension adds a new instruction sctrclr to quickly
clear the recorded entries buffer.

Signed-off-by: Rajnesh Kanwal <rkanwal@rivosinc.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20250205-b4-ctr_upstream_v6-v6-5-439d8e06c8ef@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 5a99c47b12..f156bfab12 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -485,6 +485,35 @@ void helper_ctr_add_entry(CPURISCVState *env, target_ulong src,
                         env->priv, env->virt_enabled);
 }
 
+void helper_ctr_clear(CPURISCVState *env)
+{
+    /*
+     * It's safe to call smstateen_acc_ok() for umode access regardless of the
+     * state of bit 54 (CTR bit in case of m/hstateen) of sstateen. If the bit
+     * is zero, smstateen_acc_ok() will return the correct exception code and
+     * if it's one, smstateen_acc_ok() will return RISCV_EXCP_NONE. In that
+     * scenario the U-mode check below will handle that case.
+     */
+    RISCVException ret = smstateen_acc_ok(env, 0, SMSTATEEN0_CTR);
+    if (ret != RISCV_EXCP_NONE) {
+        riscv_raise_exception(env, ret, GETPC());
+    }
+
+    if (env->priv == PRV_U) {
+        /*
+         * One corner case is when sctrclr is executed from VU-mode and
+         * mstateen.CTR = 0, in which case we are supposed to raise
+         * RISCV_EXCP_ILLEGAL_INST. This case is already handled in
+         * smstateen_acc_ok().
+         */
+        uint32_t excep = env->virt_enabled ? RISCV_EXCP_VIRT_INSTRUCTION_FAULT :
+            RISCV_EXCP_ILLEGAL_INST;
+        riscv_raise_exception(env, excep, GETPC());
+    }
+
+    riscv_ctr_clear(env);
+}
+
 void helper_wfi(CPURISCVState *env)
 {
     CPUState *cs = env_cpu(env);