target/riscv: Add step to validate 'B' extension

If the B extension is enabled warn if the user has disabled any of the
required extensions that are part of the 'B' extension. Conversely
enable the extensions that make up the 'B' extension if it is enabled.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240111161644.33630-3-rbradford@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/tcg/tcg-cpu.c

@@ -442,6 +442,35 @@ static void riscv_cpu_validate_g(RISCVCPU *cpu)
     }
 }
 
+static void riscv_cpu_validate_b(RISCVCPU *cpu)
+{
+    const char *warn_msg = "RVB mandates disabled extension %s";
+
+    if (!cpu->cfg.ext_zba) {
+        if (!cpu_cfg_ext_is_user_set(CPU_CFG_OFFSET(ext_zba))) {
+            cpu->cfg.ext_zba = true;
+        } else {
+            warn_report(warn_msg, "zba");
+        }
+    }
+
+    if (!cpu->cfg.ext_zbb) {
+        if (!cpu_cfg_ext_is_user_set(CPU_CFG_OFFSET(ext_zbb))) {
+            cpu->cfg.ext_zbb = true;
+        } else {
+            warn_report(warn_msg, "zbb");
+        }
+    }
+
+    if (!cpu->cfg.ext_zbs) {
+        if (!cpu_cfg_ext_is_user_set(CPU_CFG_OFFSET(ext_zbs))) {
+            cpu->cfg.ext_zbs = true;
+        } else {
+            warn_report(warn_msg, "zbs");
+        }
+    }
+}
+
 /*
  * Check consistency between chosen extensions while setting
  * cpu->cfg accordingly.
@@ -455,6 +484,10 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
         riscv_cpu_validate_g(cpu);
     }
 
+    if (riscv_has_ext(env, RVB)) {
+        riscv_cpu_validate_b(cpu);
+    }
+
     if (riscv_has_ext(env, RVI) && riscv_has_ext(env, RVE)) {
         error_setg(errp,
                    "I and E extensions are incompatible");