Re: [PATCH] target/riscv: Mask the implicitly enabled extensions in isa_string based on priv version

[Daniel Henrique Barboza]

On 4/7/23 00:30, Weiwei Li wrote:
> Using implicitly enabled extensions such as Zca/Zcf/Zcd instead of their
> super extensions can simplify the extension related check. However, they
> may have higher priv version than their super extensions. So we should mask
> them in the isa_string based on priv version to make them invisible to user
> if the specified priv version is lower than their minimal priv version.
>
> Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
> ---
>   target/riscv/cpu.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index cb68916fce..1a5099382c 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1709,6 +1709,7 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char 
> **isa_str,
>   
>       for (i = 0; i < ARRAY_SIZE(isa_edata_arr); i++) {
>           if (isa_edata_arr[i].multi_letter &&
> +            (cpu->env.priv_ver >= isa_edata_arr[i].min_version) &&

We don't have a way of telling whether an extension was enabled by us or by the 
user.
This will end up filtering user extensions from the isa_string.

IMHO, the way the logic is working today, we can't enable Z extensions based on 
enabled
MISA bits alone and disable extensions based on priv_spec at the same time. We 
would
need to check for priv_version when enabling these extensions implicitly during 
realize().
Another alternative is to not disable any extensions at all based on priv spec 
- we send
a warning about the priv mismatch and that's it.


Thanks,

Daniel



>               isa_ext_is_enabled(cpu, &isa_edata_arr[i])) {
>               new = g_strconcat(old, "_", isa_edata_arr[i].name, NULL);
>               g_free(old);