Re: [RFC PATCH 1/1] RISC-V: Add privileged extensions without instructions/CSRs

[Tsukasa OI <research_trasio@irq.a4lg.com>]

On 2022/09/22 18:44, Tsukasa OI via Binutils wrote:
> On 2022/09/22 17:48, Nelson Chu wrote:
>> On Thu, Sep 22, 2022 at 3:59 PM Tsukasa OI <research_trasio@irq.a4lg.com> wrote:
>>>
>>> Currently, GNU Binutils does not support following privileged extensions:
>>>
>>> -   'Smepmp'
>>> -   'Svnapot'
>>> -   'Svpbmt'
>>>
>>> as they do not provide new CSRs or new instructions ('Smepmp' extends the
>>> privileged architecture CSRs but does not define the CSR itself).  However,
>>> adding them might be useful as we no longer have to "filter" ISA strings
>>> just for toolchains (if full ISA string is given by a vendor, we can
>>> straightly use it).
>>
>> OKay.
>>
>> Nelson
> 
> Understood.  I'm going to push this patch in a week if there's no other
> comments.  But until then, I'll wait for other opinions.
> 
> Thanks,
> Tsukasa

Committed since there's no objections here.

Thanks,
Tsukasa

> 
>>
>>> And there's a fact that supports this theory: there's already an
>>> (unprivileged) extension which does not provide CSRs or instructions (but
>>> only an architectural guarantee): 'Zkt' (constant timing guarantee for
>>> certain subset of RISC-V instructions).
>>>
>>> This simple patchset simply adds three privileged extensions listed above.
>>>
>>> bfd/ChangeLog:
>>>
>>>         * elfxx-riscv.c (riscv_supported_std_s_ext): Add 'Smepmp',
>>>         'Svnapot' and 'Svpbmt' extensions.
>>> ---
>>>  bfd/elfxx-riscv.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
>>> index 7eda177bd6e..bbc30c9afc2 100644
>>> --- a/bfd/elfxx-riscv.c
>>> +++ b/bfd/elfxx-riscv.c
>>> @@ -1210,10 +1210,13 @@ static struct riscv_supported_ext riscv_supported_std_z_ext[] =
>>>
>>>  static struct riscv_supported_ext riscv_supported_std_s_ext[] =
>>>  {
>>> +  {"smepmp",           ISA_SPEC_CLASS_DRAFT,           1, 0, 0 },
>>>    {"smstateen",                ISA_SPEC_CLASS_DRAFT,           1, 0, 0 },
>>>    {"sscofpmf",         ISA_SPEC_CLASS_DRAFT,           1, 0, 0 },
>>>    {"sstc",             ISA_SPEC_CLASS_DRAFT,           1, 0, 0 },
>>>    {"svinval",          ISA_SPEC_CLASS_DRAFT,           1, 0, 0 },
>>> +  {"svnapot",          ISA_SPEC_CLASS_DRAFT,           1, 0, 0 },
>>> +  {"svpbmt",           ISA_SPEC_CLASS_DRAFT,           1, 0, 0 },
>>>    {NULL, 0, 0, 0, 0}
>>>  };
>>>
>>> --
>>> 2.34.1
>>>
>>
>