Re: [PATCH v2 04/18] target/riscv/cpu.c: restrict 'mimpid' value

[Alistair Francis]

On Wed, Jun 14, 2023 at 7:01 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> Following the same logic used with 'mvendorid' let's also restrict
> 'mimpid' for named CPUs. Generic CPUs keep setting the value freely.
>
> Note that we're getting rid of the default RISCV_CPU_MARCHID value. The
> reason is that this is not a good default since it's dynamic, changing
> with with every QEMU version, regardless of whether the actual
> implementation of the CPU changed from one QEMU version to the other.
> Named CPU should set it to a meaningful value instead and generic CPUs
> can set whatever they want.
>
> This is the error thrown for an invalid 'mimpid' value for the veyron-v1
> CPU:
>
> $ ./qemu-system-riscv64 -M virt -nographic -cpu veyron-v1,mimpid=2
> qemu-system-riscv64: can't apply global veyron-v1-riscv-cpu.mimpid=2:
>     Unable to change veyron-v1-riscv-cpu mimpid (0x111)
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/cpu.c | 34 ++++++++++++++++++++++++++++++++--
>  1 file changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 6a9a6d34eb..39c550682a 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -42,7 +42,6 @@
>  #define RISCV_CPU_MARCHID   ((QEMU_VERSION_MAJOR << 16) | \
>                               (QEMU_VERSION_MINOR << 8)  | \
>                               (QEMU_VERSION_MICRO))
> -#define RISCV_CPU_MIMPID    RISCV_CPU_MARCHID
>
>  static const char riscv_single_letter_exts[] = "IEMAFDQCPVH";
>
> @@ -1735,7 +1734,6 @@ static Property riscv_cpu_properties[] = {
>      DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true),
>
>      DEFINE_PROP_UINT64("marchid", RISCVCPU, cfg.marchid, RISCV_CPU_MARCHID),
> -    DEFINE_PROP_UINT64("mimpid", RISCVCPU, cfg.mimpid, RISCV_CPU_MIMPID),
>
>  #ifndef CONFIG_USER_ONLY
>      DEFINE_PROP_UINT64("resetvec", RISCVCPU, env.resetvec, DEFAULT_RSTVEC),
> @@ -1854,6 +1852,35 @@ static void cpu_get_mvendorid(Object *obj, Visitor *v, 
> const char *name,
>      visit_type_bool(v, name, &value, errp);
>  }
>
> +static void cpu_set_mimpid(Object *obj, Visitor *v, const char *name,
> +                           void *opaque, Error **errp)
> +{
> +    bool dynamic_cpu = riscv_cpu_is_dynamic(obj);
> +    RISCVCPU *cpu = RISCV_CPU(obj);
> +    uint64_t prev_val = cpu->cfg.mimpid;
> +    uint64_t value;
> +
> +    if (!visit_type_uint64(v, name, &value, errp)) {
> +        return;
> +    }
> +
> +    if (!dynamic_cpu && prev_val != value) {
> +        error_setg(errp, "Unable to change %s mimpid (0x%lx)",
> +                   object_get_typename(obj), prev_val);
> +        return;
> +    }
> +
> +    cpu->cfg.mimpid = value;
> +}
> +
> +static void cpu_get_mimpid(Object *obj, Visitor *v, const char *name,
> +                           void *opaque, Error **errp)
> +{
> +    bool value = RISCV_CPU(obj)->cfg.mimpid;
> +
> +    visit_type_bool(v, name, &value, errp);
> +}
> +
>  static void riscv_cpu_class_init(ObjectClass *c, void *data)
>  {
>      RISCVCPUClass *mcc = RISCV_CPU_CLASS(c);
> @@ -1888,6 +1915,9 @@ static void riscv_cpu_class_init(ObjectClass *c, void 
> *data)
>      object_class_property_add(c, "mvendorid", "uint32", cpu_get_mvendorid,
>                                cpu_set_mvendorid, NULL, NULL);
>
> +    object_class_property_add(c, "mimpid", "uint64", cpu_get_mimpid,
> +                              cpu_set_mimpid, NULL, NULL);
> +
>      device_class_set_props(dc, riscv_cpu_properties);
>  }
>
> --
> 2.40.1
>
>