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

[liweiwei]

On 2023/4/7 18:58, Daniel Henrique Barboza wrote:
> 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.

As the method described in the 
https://lists.gnu.org/archive/html/qemu-riscv/2023-04/msg00200.html:

The user specified extension have been disabled in realize(), So what 
needs masked is the implied extensions here.

> 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().

If we check this in realize(), we also need check them in support of the 
extension. So this is unnecessary.

Regards,

Weiwei Li

> 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);