Palmer,
Thank you for your input.
Our strong intention is to not change specs once frozen. I speak for the committees here and say that, in our opinion, declaring something frozen sets a very high bar for making any changes and is sufficient to allow code supporting an extension to be upstreamed. Of course if an unexpected and significant issue is discovered during the public review that absolutely must be addressed and cannot be deferred to a future extension (where the cost of not addressing the issue exceeds the cost of addressing it. for example introduces security vulnerabilities), then we will do so, as anyone should expect from a public review.
We do not have versions of extensions. If an extension has a problem once ratified, we will issue errata. All implementers have to publish the errata if they use branding. We may release a new extension with the bulk of the original extension plus the errata fix at some future date.
New extensions reserve the right to be incompatible with existing extensions but our philosophy is very much to minimize that and only allow the rare well-justified exceptions. Reasons may include errata, security issues discovered, or new functionality we need to add that justifies creating an incompatibility, etc.
What specifically do you see as an issue? What are you blocked on by our conventions? We need specific details to resolve any issues. Right now, I don't feel I have enough information from you.
Thanks
Mark
P.S. We had some situations in the past, in part due to vendors not waiting for the specification processes to conclude, where implementers implemented non-confoming chips either with vendor-specific extensions using reserved opcodes and state, or implementing early drafts of standards-track proposals in the development state (will likely change). This is in the past and resolved. Anyone implementing non-standard extensions must advertise them as such and make it clear that these are not standard RISC-V extensions: this should make it clear for upstream projects that they will be dealing with the respective vendors for support and maintenance, and that any code implementing support for these extensions will be different from what covers the respective standard extensions. Whether upstream projects accept such changes, and what conditions they stipulate for acceptance of these changes, are beyond the control of RISC-V. We also, as I have described to you many times, have instituted mandatory standards specification states for the front page of each specification to ensure clarity (any divergence from this is a bug and we work to fix these quickly).
On Tue, Sep 28, 2021 at 11:34 AM Palmer Dabbelt palmer@dabbelt.com wrote:
On Mon, 27 Sep 2021 08:57:15 PDT (-0700), markhimelstein@riscv.org wrote:
the words in this document :
https://wiki.riscv.org/plugins/servlet/mobile?contentId=13098230#content/vie...
make it very clear when changes are allowed or not and likely or not.
if you think the verbiage is somehow ambiguous please help us make it
better.
I'm not really worried about changes, I'm worried about a committment to future compatibility. When we take code into the kernel (and most other core systems projects) we're taking on the burden of supporting (until someone can prove there are no more users), which is very difficult to do when the ISA changes in an incompatible fashion. The whole point of agreeing on the frozen thing was that it gave us a committment from the specifcation authors that the future ISA would be compatible with th frozen extensions.
We're already in this spot with the V extension and the whole stable thing, this definitaion of frozen looks very much like what was has led to the issues there. Saying the spec won't change really isn't meaningful, it's saying future specs will be compatible that's important. Nothing in this whole rule touches on compatibility, and I really don't want to end up in a bigger mess than we're already in.
(Also: some PGE subcontractor drove a crane into my house, so things are a bit chaotic on my end. If you have that list of what's officially frozen, can you send it out? I'll try to take a look ASAP, as then I can at least focus the discussion on what's relevant right now.)
Mark
sent from a mobile device. please forgive any typos.
On Sep 27, 2021, at 8:50 AM, Palmer Dabbelt palmer@dabbelt.com wrote:
On Tue, 21 Sep 2021 17:20:17 PDT (-0700), atishp@atishpatra.org wrote:
Hi All, Please find the below email from Stephano about the freeze
announcement for
various RISC-V specifications that will be part of privilege
specification
v1.12. All the review discussions are happening in the isa-dev mailing list.
The
review period will be open for 45 days ending Sunday October 31, 2021.
I just want to highlight the fact that the *H*, *V, SvPBMT, CMO
extensions
are frozen now. *This will help us merge some patches that have been present in the mailing list for a while.
Here are the ratification policy and extension life cycle documents
present
in the public. If you have any questions regarding this, please check
with
Mark/Stephano (cc'd).
Ratification policy:
https://docs.google.com/document/d/1-UlaSGqk59_myeuPMrV9gyuaIgnmFzGh5Gfy_tpV...
Extension life cycle:
https://docs.google.com/presentation/d/1nQ5uFb39KA6gvUi5SReWfIQSiRN7hp6z7ZPf...
I'm still buried after Plumbers, but one of the bits on my TODO list
was to look throught the new definitions for frozen and stable. Nothing in this extension life cycle talks about the point at which compatibility will be maintained, which was really the central point behind frozen before.
Are there more concrete definitions somewhere?