Re: Public review of Supervisor Binary Interface (SBI) Specification

Anup Patel

HI Andrew,

On Wed, Jan 19, 2022 at 6:31 AM Andrew Waterman <andrew@...> wrote:

Hi Atish,

I've got some minor feedback from the Architecture Review committee:

We think that only the RV64 SBI should be ratified at this time. The RV32 variants are likely to need some reworking (e.g., passing a physical address as an unsigned long precludes use of the full 34-bit physical-address space), and the RV32 variants aren't currently in high demand, anyway.
The RV32 physical address space limitation only impacts SBI RFENCE
calls and SBI HSM calls. A RV32 system can still use these calls as
long as their physical address space is within 4GB.

I suggest we document this RV32 limitation in SBI RFENCE and SBI HSM
chapters for SBI v1.0 and plan to address this in SBI v2.0.

It would be helpful to add some non-normative text about what the SBI assumes about discovery. For example, there's no SBI call to retrieve the value of the misa CSR--which is reasonable because the OS is presumably expected to retrieve this information from the DeviceTree--but readers who don't know that might find this surprising.
I agree with this suggestion. We got this question multiple times in
the past as well.



On Wed, Jan 12, 2022 at 10:43 AM <atishp@...> wrote:

I just realized that the below email was not delivered to unix
platform mailing list and
linux-riscv mailing list because of the attachment. Reseeding it again
without the
attachment. Apologies for the noise.

We are delighted to announce the start of the public review period for
the Non-ISA Supervisor Binary Interface (SBI) specification. The
SBI specification is considered as frozen now as per the RISC-V International

The review period begins today, Monday Jan 10, and ends on Monday
Jan 24 (inclusive).

The specification can be found here

which was generated from the source available in the following GitHub

To respond to the public review, please either reply to this email or
send comments to the platform mailing list[1] or add issues to the
SBI GitHub repo[2]. We welcome all input and appreciate your time and
effort in helping us by reviewing the specification.

During the public review period, corrections, comments, and
suggestions, will be gathered for review by the Platform HSC members. Any
minor corrections and/or uncontroversial changes will be incorporated
into the specification. Any remaining issues or proposed changes will
be addressed in the public review summary report. If there are no
issues that require incompatible changes to the public review
specification, the platform HSC will recommend the updated
specifications be approved and ratified by the RISC-V Technical
Steering Committee and the RISC-V Board of Directors.

SBI specification is non-ISA specifications and will evolve over time
with new extensions as long as they are backward compatible. Any such
proposals for new extensions can be included in the future releases
after proper discussions in the platform working group meetings.

Thanks to all the contributors for all their hard work.

[1] tech-unixplatformspec@...

Atish Patra

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