> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 0bbfd7f4574..bc29e118c6d 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -438,6 +438,9 @@ static void riscv_cpu_realize(DeviceState *dev, Error
> **errp)
> if (cpu->cfg.ext_h) {
> target_misa |= RVH;
> }
> + if (cpu->cfg.ext_b) {
> + target_misa |= RVB;
> + }
> if (cpu->cfg.ext_v) {
> target_misa |= RVV;
> if (!is_power_of_2(cpu->cfg.vlen)) {
> @@ -515,6 +518,7 @@ static Property riscv_cpu_properties[] = {
> DEFINE_PROP_BOOL("s", RISCVCPU, cfg.ext_s, true),
> DEFINE_PROP_BOOL("u", RISCVCPU, cfg.ext_u, true),
> /* This is experimental so mark with 'x-' */
> + DEFINE_PROP_BOOL("x-b", RISCVCPU, cfg.ext_b, true),
I think the default value should be false?
> DEFINE_PROP_BOOL("x-h", RISCVCPU, cfg.ext_h, false),
> DEFINE_PROP_BOOL("x-v", RISCVCPU, cfg.ext_v, false),
> DEFINE_PROP_BOOL("Counters", RISCVCPU, cfg.ext_counters, true),
