Re: [PATCH v9 17/20] target/riscv/cpu.c: create KVM mock properties

[Alistair Francis]

On Thu, Jul 6, 2023 at 8:19 PM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> KVM-specific properties are being created inside target/riscv/kvm.c. But
> at this moment we're gathering all the remaining properties from TCG and
> adding them as is when running KVM. This creates a situation where
> non-KVM properties are setting flags to 'true' due to its default
> settings (e.g.  Zawrs). Users can also freely enable them via command
> line.
>
> This doesn't impact runtime per se because KVM doesn't care about these
> flags, but code such as riscv_isa_string_ext() take those flags into
> account. The result is that, for a KVM guest, setting non-KVM properties
> will make them appear in the riscv,isa DT.
>
> We want to keep the same API for both TCG and KVM and at the same time,
> when running KVM, forbid non-KVM extensions to be enabled internally. We
> accomplish both by changing riscv_cpu_add_user_properties() to add a
> mock boolean property for every non-KVM extension in
> riscv_cpu_extensions[]. Then, when running KVM, users are still free to
> set extensions at will, but we'll error out if a non-KVM extension is
> enabled. Setting such extension to 'false' will be ignored.
>
> 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 | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 2acf77949f..b2883ca533 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1840,6 +1840,26 @@ static Property riscv_cpu_extensions[] = {
>      DEFINE_PROP_END_OF_LIST(),
>  };
>
> +
> +#ifndef CONFIG_USER_ONLY
> +static void cpu_set_cfg_unavailable(Object *obj, Visitor *v,
> +                                    const char *name,
> +                                    void *opaque, Error **errp)
> +{
> +    const char *propname = opaque;
> +    bool value;
> +
> +    if (!visit_type_bool(v, name, &value, errp)) {
> +        return;
> +    }
> +
> +    if (value) {
> +        error_setg(errp, "extension %s is not available with KVM",
> +                   propname);
> +    }
> +}
> +#endif
> +
>  /*
>   * Add CPU properties with user-facing flags.
>   *
> @@ -1868,6 +1888,22 @@ static void riscv_cpu_add_user_properties(Object *obj)
>              if (object_property_find(obj, prop->name)) {
>                  continue;
>              }
> +
> +            /*
> +             * Set the default to disabled for every extension
> +             * unknown to KVM and error out if the user attempts
> +             * to enable any of them.
> +             *
> +             * We're giving a pass for non-bool properties since they're
> +             * not related to the availability of extensions and can be
> +             * safely ignored as is.
> +             */
> +            if (prop->info == &qdev_prop_bool) {
> +                object_property_add(obj, prop->name, "bool",
> +                                    NULL, cpu_set_cfg_unavailable,
> +                                    NULL, (void *)prop->name);
> +                continue;
> +            }
>          }
>  #endif
>          qdev_property_add_static(dev, prop);
> --
> 2.41.0
>
>