Re: [PATCH v3] dt-bindings: riscv: deprecate riscv,isa

From: Anup Patel
Date: Thu Jun 29 2023 - 02:46:17 EST

On Thu, Jun 29, 2023 at 8:49 AM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
>
> On Wed, 28 Jun 2023 08:31:32 PDT (-0700), apatel@xxxxxxxxxxxxxxxx wrote:
> > On Wed, Jun 28, 2023 at 7:46 PM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
> >>
> >> On Tue, 27 Jun 2023 08:49:06 PDT (-0700), Palmer Dabbelt wrote:
> >> > On Mon, 26 Jun 2023 23:52:06 PDT (-0700), apatel@xxxxxxxxxxxxxxxx wrote:
> >> >> On Tue, Jun 27, 2023 at 1:23 AM Palmer Dabbelt <palmer@xxxxxxxxxxxx> wrote:
> >> >>>
> >> >>> On Mon, 26 Jun 2023 10:38:43 PDT (-0700), apatel@xxxxxxxxxxxxxxxx wrote:
> >> >>> > On Mon, Jun 26, 2023 at 3:42 PM Conor Dooley <conor.dooley@xxxxxxxxxxxxx> wrote:
> >> >>> >>
> >> >>> >> intro
> >> >>> >> =====
> >> >>> >>
> >> >>> >> When the RISC-V dt-bindings were accepted upstream in Linux, the base
> >> >>> >> ISA etc had yet to be ratified. By the ratification of the base ISA,
> >> >>> >> incompatible changes had snuck into the specifications - for example the
> >> >>> >> Zicsr and Zifencei extensions were spun out of the base ISA.
> >> >>> >>
> >> >>> >> Fast forward to today, and the reason for this patch.
> >> >>> >> Currently the riscv,isa dt property permits only a specific subset of
> >> >>> >> the ISA string - in particular it excludes version numbering.
> >> >>> >> With the current constraints, it is not possible to discern whether
> >> >>> >> "rv64i" means that the hart supports the fence.i instruction, for
> >> >>> >> example.
> >> >>> >> Future systems may choose to implement their own instruction fencing,
> >> >>> >> perhaps using a vendor extension, or they may not implement the optional
> >> >>> >> counter extensions. Software needs a way to determine this.
> >> >>> >>
> >> >>> >> versioning schemes
> >> >>> >> ==================
> >> >>> >>
> >> >>> >> "Use the extension versions that are described in the ISA manual" you
> >> >>> >> may say, and it's not like this has not been considered.
> >> >>> >> Firstly, software that parses the riscv,isa property at runtime will
> >> >>> >> need to contain a lookup table of some sort that maps arbitrary versions
> >> >>> >> to versions it understands. There is not a consistent application of
> >> >>> >> version number applied to extensions, with a higgledy-piggledy
> >> >>> >> collection of tags, "bare" and versioned documents awaiting the reader
> >> >>> >> on the "recently ratified extensions" page:
> >> >>> >> https://wiki.riscv.org/display/HOME/Recently+Ratified+Extensions
> >> >>> >>
> >> >>> >> As an aside, and this is reflected in the patch too, since many
> >> >>> >> extensions have yet to appear in a release of the ISA specs,
> >> >>> >> they are defined by commits in their respective "working draft"
> >> >>> >> repositories.
> >> >>> >>
> >> >>> >> Secondly, there is an issue of backwards compatibility, whereby allowing
> >> >>> >> numbers in the ISA string, some parsers may be broken. This would
> >> >>> >> require an additional property to be created to even use the versions in
> >> >>> >> this manner.
> >> >>> >>
> >> >>> >> ~boolean properties~ string array property
> >> >>> >> ==========================================
> >> >>> >>
> >> >>> >> If a new property is needed, the whole approach may as well be looked at
> >> >>> >> from the bottom up. A string with limited character choices etc is
> >> >>> >> hardly the best approach for communicating extension information to
> >> >>> >> software.
> >> >>> >>
> >> >>> >> Switching to using properties that are defined on a per extension basis,
> >> >>> >> allows us to define explicit meanings for the DT representation of each
> >> >>> >> extension - rather than the current situation where different operating
> >> >>> >> systems or other bits of software may impart different meanings to
> >> >>> >> characters in the string.
> >> >>> >> Clearly the best source of meanings is the specifications themselves,
> >> >>> >> this just provides us the ability to choose at what point in time the
> >> >>> >> meaning is set. If an extension changes incompatibility in the future,
> >> >>> >> a new property will be required.
> >> >>> >>
> >> >>> >> Off-list, some of the RVI folks have committed to shoring up the wording
> >> >>> >> in either the ISA specifications, the riscv-isa-manual or
> >> >>> >> so that in the future, modifications to and additions or removals of
> >> >>> >> features will require a new extension. Codifying that assertion
> >> >>> >> somewhere would make it quite unlikely that compatibility would be
> >> >>> >> broken, but we have the tools required to deal with it, if & when it
> >> >>> >> crops up.
> >> >>> >> It is in our collective interest, as consumers of extension meanings, to
> >> >>> >> define a scheme that enforces compatibility.
> >> >>> >>
> >> >>> >> The use of individual properties, rather than elements in a single
> >> >>> >> string, will also permit validation that the properties have a meaning,
> >> >>> >> as well as potentially reject mutually exclusive combinations, or
> >> >>> >> enforce dependencies between extensions. That would not have be possible
> >> >>> >> with the current dt-schema infrastructure for arbitrary strings, as we
> >> >>> >> would need to add a riscv,isa parser to dt-validate!
> >> >>> >> That's not implemented in this patch, but rather left as future work (for
> >> >>> >> the brave, or the foolish).
> >> >>> >>
> >> >>> >> acpi
> >> >>> >> ====
> >> >>> >>
> >> >>> >> The current ACPI ECR is based on having a single ISA string unfortunately,
> >> >>> >> but ideally ACPI will move to another method, perhaps GUIDs, that give
> >> >>> >> explicit meaning to extensions.
> >> >>> >
> >> >>> > Drop this paragraph on ACPI.
> >> >>> >
> >> >>> > We clearly mentioned previously that ACPI will follow specs defined by RVI.
> >> >>> > There are scalability issues in using GUIDs for each ISA extension.
> >> >>>
> >> >>> Which spec are we following for the ACPI ISA string?
> >> >>
> >> >> ACPI RHCT follows the "ISA Extension Naming Conventions"
> >> >> defined by the RISC-V unpriv spec. I understand that there are
> >> >> unresolved issues in the "ISA Extension Naming Conventions"
> >> >> which should be addressed by RVI and we should also try our
> >> >> best to have this fixed in the spec.
> >> >
> >> > Which version of the spec? We've had a ton of issues related to
> >> > versioning everywhere else the ISA string has been used, we need to know
> >> > specifically which version we're parsing in order to do anything
> >> > meaningful with it.
> >>
> >> Anup: Can you please provide a pointer to the spec this is supposed to
> >> implement? I don't want to end up in the same spot again where we're
> >> presuming some spec changes, we've got to support whatever we merge no
> >> matter what happens on the spec side.
> >>
> >> In theory I'm on vacation today, but I'll try and look at the thread
> >> again tonight when I get back.
> >
> > It is the "Chapter 29. ISA Extension Naming Conventions" of the
> > RISC-V unpriv specification.
> > (https://github.com/riscv/riscv-isa-manual/releases/download/riscv-isa-release-1239329-2023-05-23/unpriv-isa-asciidoc.pdf)
> >
> > The RISC-V unpriv specification is only a collection of extensions
> > hence it does not have its own version.
>
> There's a version right on the front page, it says "Version ASCIIDOC
> Conversion, 12/2022". There's a few with that version, but versioning
> is pretty broken in RISC-V land so we've mostly just started running
> with the commits/tags.
>
> It also says it's a pre release version, but if that's what ACPI is
> using then I'm fine with it -- the key is that whatever we're supporting
> we're stuck with, as we have to maintain compatibility here.
>
> > We should work with RVI to address the concerns/clarifications
> > that we need in "Chapter 29. ISA Extension Naming Conventions".
> >
> > We can also create GitHub issues for unpriv spec if that helps.
>
> The nice thing about starting with a new interface is that there's
> nothing to be compatible with, so there's no issues. Given what a mess
> ISA strings have been everywhere else I'm sure we'll have some, but
> that's problem for later.
>
> I couldn't find anywhere else this was written down, so I started an
> ACPI doc -- as usual maybe a bit odd for just the one thing, but we
> usually end up with more.
>
> https://lore.kernel.org/r/20230629031705.15575-1-palmer@xxxxxxxxxxxx/

The "ISA string node structure" does mention that "ISA string" is
"Null-terminated ASCII Instruction Set Architecture (ISA) string for this
hart. The format of the ISA string is defined in the RISC-V unprivileged
specification."
(Refer, page6 of
https://docs.google.com/document/d/1zSw9eaW3tlrdGxkclo9FsLvYxUvhAjRCR8_71EfRJR4/edit?usp=sharing)

Currently, the ACPI spec does not mention the exact version of the
"ISA string" chapter in the RISC-V unprivileged specification which
can be improved.

Also, there is a 2-byte "revision" field in the "ISA string node structure"
which can be used in the future to specify a different version of the
"ISA string" chapter.

Regards,
Anup

>
>
> > Regards,
> > Anup
> >
> >>
> >> >> In any case, ACPI spec is owned by UEFI forum so it does
> >> >> not make sense to define/recommend anything for ACPI in
> >> >> DT bindings.
> >> >
> >> > Unless I missed something this is just a long commit message, it's not
> >> > even in the docs. If you don't want the DT side to even mention ACPI
> >> > that's fine with me, though, I don't really care.
> >> >
> >> >>
> >> >> Regards,
> >> >> Anup
> >> >>
> >> >>
> >> >>
> >> >>>
> >> >>> > Regards,
> >> >>> > Anup
> >> >>> >
> >> >>> >>
> >> >>> >> parser simplicity
> >> >>> >> =================
> >> >>> >>
> >> >>> >> Many systems that parse DT at runtime already implement an function that
> >> >>> >> can check for the presence of a string in an array of string, as it is
> >> >>> >> similar to the process for parsing a list of compatible strings, so a
> >> >>> >> bunch of new, custom, DT parsing should not be needed.
> >> >>> >> Getting rid of "riscv,isa" parsing would be a nice simplification, but
> >> >>> >> unfortunately for backwards compatibility with old dtbs, existing
> >> >>> >> parsers may not be removable - which may greatly simplify
> >> >>> >> dt parsing code. In Linux, for example, checking for whether a hart
> >> >>> >> supports an extension becomes as simple as:
> >> >>> >> of_property_match_string(node, "riscv,isa-extensions", "zicbom")
> >> >>> >>
> >> >>> >> vendor extensions
> >> >>> >> =================
> >> >>> >>
> >> >>> >> Compared to riscv,isa, this proposed scheme promotes vendor extensions,
> >> >>> >> oft touted as the strength of RISC-V, to first-class citizens.
> >> >>> >> At present, extensions are defined as meaning what the RISC-V ISA
> >> >>> >> specifications say they do. There is no realistic way of using that
> >> >>> >> interface to provide cross-platform definitions for what vendor
> >> >>> >> extensions mean. Vendor extensions may also have even less consistency
> >> >>> >> than RVI do in terms of versioning, or no care about backwards
> >> >>> >> compatibility.
> >> >>> >> The new property allows us to assign explicit meanings on a per vendor
> >> >>> >> extension basis, backed up by a description of their meanings.
> >> >>> >>
> >> >>> >> fin
> >> >>> >> ===
> >> >>> >>
> >> >>> >> Create a new file to store the extension meanings and a new
> >> >>> >> riscv,isa-base property to replace the aspect of riscv,isa that is
> >> >>> >> not represented by the new property - the base ISA implemented by a hart.
> >> >>> >>
> >> >>> >> As a starting point, add properties for extensions currently used in
> >> >>> >> Linux.
> >> >>> >>
> >> >>> >> Finally, mark riscv,isa as deprecated, as removing support for it in
> >> >>> >> existing programs would be an ABI break.
> >> >>> >>
> >> >>> >> CC: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> >> >>> >> CC: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> >> >>> >> CC: Rob Herring <robh+dt@xxxxxxxxxx>
> >> >>> >> CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>
> >> >>> >> CC: Alistair Francis <alistair.francis@xxxxxxx>
> >> >>> >> CC: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> >> >>> >> CC: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> >> >>> >> CC: Atish Patra <atishp@xxxxxxxxxxxxxx>
> >> >>> >> CC: Jessica Clarke <jrtc27@xxxxxxxxxx>
> >> >>> >> CC: Rick Chen <rick@xxxxxxxxxxxxx>
> >> >>> >> CC: Leo <ycliang@xxxxxxxxxxxxx>
> >> >>> >> CC: Oleksii <oleksii.kurochko@xxxxxxxxx>
> >> >>> >> CC: linux-riscv@xxxxxxxxxxxxxxxxxxx
> >> >>> >> CC: qemu-riscv@xxxxxxxxxx
> >> >>> >> CC: u-boot@xxxxxxxxxxxxx
> >> >>> >> CC: devicetree@xxxxxxxxxxxxxxx
> >> >>> >> CC: linux-kernel@xxxxxxxxxxxxxxx
> >> >>> >> Reviewed-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> >> >>> >> Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> >> >>> >> Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> >> >>> >> ---
> >> >>> >> Changes in v3:
> >> >>> >> - Per Rob's suggestion, switch to an array of strings. Cuts down on the
> >> >>> >> size, compared to booleans. It has a standard mechanism for parsing
> >> >>> >> (you need to parse arrays of strings for compatibles). It still allows
> >> >>> >> for having a limited set of explicitly defined properties - so the
> >> >>> >> advantages over a free-form string still apply.
> >> >>> >> - Pick up Palmer's Ack and Review (although I expect that he will be the
> >> >>> >> one to apply this).
> >> >>> >> ---
> >> >>> >> .../devicetree/bindings/riscv/cpus.yaml | 43 ++-
> >> >>> >> .../devicetree/bindings/riscv/extensions.yaml | 245 ++++++++++++++++++
> >> >>> >> 2 files changed, 265 insertions(+), 23 deletions(-)
> >> >>> >> create mode 100644 Documentation/devicetree/bindings/riscv/extensions.yaml
> >> >>> >>
> >> >>> >> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> >> >>> >> index 67bd239ead0b..74bc92591086 100644
> >> >>> >> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> >> >>> >> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> >> >>> >> @@ -25,6 +25,7 @@ description: |
> >> >>> >>
> >> >>> >> allOf:
> >> >>> >> - $ref: /schemas/cpu.yaml#
> >> >>> >> + - $ref: extensions.yaml
> >> >>> >>
> >> >>> >> properties:
> >> >>> >> compatible:
> >> >>> >> @@ -82,25 +83,6 @@ properties:
> >> >>> >> description:
> >> >>> >> The blocksize in bytes for the Zicboz cache operations.
> >> >>> >>
> >> >>> >> - riscv,isa:
> >> >>> >> - description:
> >> >>> >> - Identifies the specific RISC-V instruction set architecture
> >> >>> >> - supported by the hart. These are documented in the RISC-V
> >> >>> >> - User-Level ISA document, available from
> >> >>> >> - https://riscv.org/specifications/
> >> >>> >> -
> >> >>> >> - Due to revisions of the ISA specification, some deviations
> >> >>> >> - have arisen over time.
> >> >>> >> - Notably, riscv,isa was defined prior to the creation of the
> >> >>> >> - Zicntr, Zicsr, Zifencei and Zihpm extensions and thus "i"
> >> >>> >> - implies "zicntr_zicsr_zifencei_zihpm".
> >> >>> >> -
> >> >>> >> - While the isa strings in ISA specification are case
> >> >>> >> - insensitive, letters in the riscv,isa string must be all
> >> >>> >> - lowercase.
> >> >>> >> - $ref: /schemas/types.yaml#/definitions/string
> >> >>> >> - pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:[hsxz](?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> >> >>> >> -
> >> >>> >> # RISC-V has multiple properties for cache op block sizes as the sizes
> >> >>> >> # differ between individual CBO extensions
> >> >>> >> cache-op-block-size: false
> >> >>> >> @@ -139,8 +121,17 @@ properties:
> >> >>> >> DMIPS/MHz, relative to highest capacity-dmips-mhz
> >> >>> >> in the system.
> >> >>> >>
> >> >>> >> +oneOf:
> >> >>> >> + - required:
> >> >>> >> + - riscv,isa
> >> >>> >> + - required:
> >> >>> >> + - riscv,isa-base
> >> >>> >> +
> >> >>> >> +dependencies:
> >> >>> >> + riscv,isa-base: [ "riscv,isa-extensions" ]
> >> >>> >> + riscv,isa-extensions: [ "riscv,isa-base" ]
> >> >>> >> +
> >> >>> >> required:
> >> >>> >> - - riscv,isa
> >> >>> >> - interrupt-controller
> >> >>> >>
> >> >>> >> unevaluatedProperties: false
> >> >>> >> @@ -160,7 +151,9 @@ examples:
> >> >>> >> i-cache-sets = <128>;
> >> >>> >> i-cache-size = <16384>;
> >> >>> >> reg = <0>;
> >> >>> >> - riscv,isa = "rv64imac";
> >> >>> >> + riscv,isa-base = "rv64i";
> >> >>> >> + riscv,isa-extensions = "i", "m", "a", "c";
> >> >>> >> +
> >> >>> >> cpu_intc0: interrupt-controller {
> >> >>> >> #interrupt-cells = <1>;
> >> >>> >> compatible = "riscv,cpu-intc";
> >> >>> >> @@ -183,8 +176,10 @@ examples:
> >> >>> >> i-tlb-size = <32>;
> >> >>> >> mmu-type = "riscv,sv39";
> >> >>> >> reg = <1>;
> >> >>> >> - riscv,isa = "rv64imafdc";
> >> >>> >> tlb-split;
> >> >>> >> + riscv,isa-base = "rv64i";
> >> >>> >> + riscv,isa-extensions = "i", "m", "a", "f", "d", "c";
> >> >>> >> +
> >> >>> >> cpu_intc1: interrupt-controller {
> >> >>> >> #interrupt-cells = <1>;
> >> >>> >> compatible = "riscv,cpu-intc";
> >> >>> >> @@ -202,8 +197,10 @@ examples:
> >> >>> >> device_type = "cpu";
> >> >>> >> reg = <0>;
> >> >>> >> compatible = "riscv";
> >> >>> >> - riscv,isa = "rv64imafdc";
> >> >>> >> mmu-type = "riscv,sv48";
> >> >>> >> + riscv,isa-base = "rv64i";
> >> >>> >> + riscv,isa-extensions = "i", "m", "a", "f", "d", "c";
> >> >>> >> +
> >> >>> >> interrupt-controller {
> >> >>> >> #interrupt-cells = <1>;
> >> >>> >> interrupt-controller;
> >> >>> >> diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
> >> >>> >> new file mode 100644
> >> >>> >> index 000000000000..af98307f2c2c
> >> >>> >> --- /dev/null
> >> >>> >> +++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
> >> >>> >> @@ -0,0 +1,245 @@
> >> >>> >> +# SPDX-License-Identifier: (GPL-2.0 OR MIT)
> >> >>> >> +%YAML 1.2
> >> >>> >> +---
> >> >>> >> +$id: http://devicetree.org/schemas/riscv/extensions.yaml#
> >> >>> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> >>> >> +
> >> >>> >> +title: RISC-V ISA extensions
> >> >>> >> +
> >> >>> >> +maintainers:
> >> >>> >> + - Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> >> >>> >> + - Palmer Dabbelt <palmer@xxxxxxxxxx>
> >> >>> >> + - Conor Dooley <conor@xxxxxxxxxx>
> >> >>> >> +
> >> >>> >> +description: |
> >> >>> >> + RISC-V has a large number of extensions, some of which are "standard"
> >> >>> >> + extensions, meaning they are ratified by RISC-V International, and others
> >> >>> >> + are "vendor" extensions.
> >> >>> >> + This document defines properties that indicate whether a hart supports a
> >> >>> >> + given extension.
> >> >>> >> +
> >> >>> >> + Once a standard extension has been ratified, no changes in behaviour can be
> >> >>> >> + made without the creation of a new extension.
> >> >>> >> + The properties for standard extensions therefore map to their originally
> >> >>> >> + ratified states, with the exception of the I, Zicntr & Zihpm extensions.
> >> >>> >> + See the "i" property for more information.
> >> >>> >> +
> >> >>> >> +select:
> >> >>> >> + properties:
> >> >>> >> + compatible:
> >> >>> >> + contains:
> >> >>> >> + const: riscv
> >> >>> >> +
> >> >>> >> +properties:
> >> >>> >> + riscv,isa:
> >> >>> >> + description:
> >> >>> >> + Identifies the specific RISC-V instruction set architecture
> >> >>> >> + supported by the hart. These are documented in the RISC-V
> >> >>> >> + User-Level ISA document, available from
> >> >>> >> + https://riscv.org/specifications/
> >> >>> >> +
> >> >>> >> + Due to revisions of the ISA specification, some deviations
> >> >>> >> + have arisen over time.
> >> >>> >> + Notably, riscv,isa was defined prior to the creation of the
> >> >>> >> + Zicntr, Zicsr, Zifencei and Zihpm extensions and thus "i"
> >> >>> >> + implies "zicntr_zicsr_zifencei_zihpm".
> >> >>> >> +
> >> >>> >> + While the isa strings in ISA specification are case
> >> >>> >> + insensitive, letters in the riscv,isa string must be all
> >> >>> >> + lowercase.
> >> >>> >> + $ref: /schemas/types.yaml#/definitions/string
> >> >>> >> + pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:[hsxz](?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> >> >>> >> + deprecated: true
> >> >>> >> +
> >> >>> >> + riscv,isa-base:
> >> >>> >> + description:
> >> >>> >> + The base ISA implemented by this hart, as described by the 20191213
> >> >>> >> + version of the unprivileged ISA specification.
> >> >>> >> + enum:
> >> >>> >> + - rv32i
> >> >>> >> + - rv64i
> >> >>> >> +
> >> >>> >> + riscv,isa-extensions:
> >> >>> >> + $ref: /schemas/types.yaml#/definitions/string-array
> >> >>> >> + minItems: 1
> >> >>> >> + description: Extensions supported by the hart.
> >> >>> >> + items:
> >> >>> >> + anyOf:
> >> >>> >> + # single letter extensions, in canonical order
> >> >>> >> + - const: i
> >> >>> >> + description: |
> >> >>> >> + The base integer instruction set, as ratified in the 20191213
> >> >>> >> + version of the unprivileged ISA specification, with the exception of
> >> >>> >> + counter access.
> >> >>> >> + Counter access was removed after the ratification of the 20191213
> >> >>> >> + version of the unprivileged specification and shunted into the
> >> >>> >> + Zicntr and Zihpm extensions.
> >> >>> >> +
> >> >>> >> + - const: m
> >> >>> >> + description:
> >> >>> >> + The standard M extension for integer multiplication and division, as
> >> >>> >> + ratified in the 20191213 version of the unprivileged ISA
> >> >>> >> + specification.
> >> >>> >> +
> >> >>> >> + - const: a
> >> >>> >> + description:
> >> >>> >> + The standard A extension for atomic instructions, as ratified in the
> >> >>> >> + 20191213 version of the unprivileged ISA specification.
> >> >>> >> +
> >> >>> >> + - const: f
> >> >>> >> + description:
> >> >>> >> + The standard F extension for single-precision floating point, as
> >> >>> >> + ratified in the 20191213 version of the unprivileged ISA
> >> >>> >> + specification.
> >> >>> >> +
> >> >>> >> + - const: d
> >> >>> >> + description:
> >> >>> >> + The standard D extension for double-precision floating-point, as
> >> >>> >> + ratified in the 20191213 version of the unprivileged ISA
> >> >>> >> + specification.
> >> >>> >> +
> >> >>> >> + - const: q
> >> >>> >> + description:
> >> >>> >> + The standard Q extension for quad-precision floating-point, as
> >> >>> >> + ratified in the 20191213 version of the unprivileged ISA
> >> >>> >> + specification.
> >> >>> >> +
> >> >>> >> + - const: c
> >> >>> >> + description:
> >> >>> >> + The standard C extension for compressed instructions, as ratified in
> >> >>> >> + the 20191213 version of the unprivileged ISA specification.
> >> >>> >> +
> >> >>> >> + - const: v
> >> >>> >> + description:
> >> >>> >> + The standard V extension for vector operations, as ratified
> >> >>> >> + in-and-around commit 7a6c8ae ("Fix text that describes vfmv.v.f
> >> >>> >> + encoding") of the riscv-v-spec.
> >> >>> >> +
> >> >>> >> + - const: h
> >> >>> >> + description:
> >> >>> >> + The standard H extension for hypervisors as ratified in the 20191213
> >> >>> >> + version of the privileged ISA specification.
> >> >>> >> +
> >> >>> >> + # multi-letter extensions, sorted alphanumerically
> >> >>> >> + - const: smaia
> >> >>> >> + description: |
> >> >>> >> + The standard Smaia supervisor-level extension for the advanced
> >> >>> >> + interrupt architecture for machine-mode-visible csr and behavioural
> >> >>> >> + changes to interrupts as frozen at commit ccbddab ("Merge pull
> >> >>> >> + request #42 from riscv/jhauser-2023-RC4") of riscv-aia.
> >> >>> >> +
> >> >>> >> + - const: ssaia
> >> >>> >> + description: |
> >> >>> >> + The standard Ssaia supervisor-level extension for the advanced
> >> >>> >> + interrupt architecture for supervisor-mode-visible csr and
> >> >>> >> + behavioural changes to interrupts as frozen at commit ccbddab
> >> >>> >> + ("Merge pull request #42 from riscv/jhauser-2023-RC4") of riscv-aia.
> >> >>> >> +
> >> >>> >> + - const: sscofpmf
> >> >>> >> + description: |
> >> >>> >> + The standard Sscofpmf supervisor-level extension for count overflow
> >> >>> >> + and mode-based filtering as ratified at commit 01d1df0 ("Add ability
> >> >>> >> + to manually trigger workflow. (#2)") of riscv-count-overflow.
> >> >>> >> +
> >> >>> >> + - const: sstc
> >> >>> >> + description: |
> >> >>> >> + The standard Sstc supervisor-level extension for time compare as
> >> >>> >> + ratified at commit 3f9ed34 ("Add ability to manually trigger
> >> >>> >> + workflow. (#2)") of riscv-time-compare.
> >> >>> >> +
> >> >>> >> + - const: svinval
> >> >>> >> + description:
> >> >>> >> + The standard Svinval supervisor-level extension for fine-grained
> >> >>> >> + address-translation cache invalidation as ratified in the 20191213
> >> >>> >> + version of the privileged ISA specification.
> >> >>> >> +
> >> >>> >> + - const: svnapot
> >> >>> >> + description:
> >> >>> >> + The standard Svnapot supervisor-level extensions for napot
> >> >>> >> + translation contiguity as ratified in the 20191213 version of the
> >> >>> >> + privileged ISA specification.
> >> >>> >> +
> >> >>> >> + - const: svpbmt
> >> >>> >> + description:
> >> >>> >> + The standard Svpbmt supervisor-level extensions for page-based
> >> >>> >> + memory types as ratified in the 20191213 version of the privileged
> >> >>> >> + ISA specification.
> >> >>> >> +
> >> >>> >> + - const: zba
> >> >>> >> + description: |
> >> >>> >> + The standard Zba bit-manipulation extension for address generation
> >> >>> >> + acceleration instructions as ratified at commit 6d33919 ("Merge pull
> >> >>> >> + request #158 from hirooih/clmul-fix-loop-end-condition") of
> >> >>> >> + riscv-bitmanip.
> >> >>> >> +
> >> >>> >> + - const: zbb
> >> >>> >> + description: |
> >> >>> >> + The standard Zbb bit-manipulation extension for basic bit-manipulation
> >> >>> >> + as ratified at commit 6d33919 ("Merge pull request #158 from
> >> >>> >> + hirooih/clmul-fix-loop-end-condition") of riscv-bitmanip.
> >> >>> >> +
> >> >>> >> + - const: zbc
> >> >>> >> + description: |
> >> >>> >> + The standard Zbc bit-manipulation extension for carry-less
> >> >>> >> + multiplication as ratified at commit 6d33919 ("Merge pull request
> >> >>> >> + #158 from hirooih/clmul-fix-loop-end-condition") of riscv-bitmanip.
> >> >>> >> +
> >> >>> >> + - const: zbs
> >> >>> >> + description: |
> >> >>> >> + The standard Zbs bit-manipulation extension for single-bit
> >> >>> >> + instructions as ratified at commit 6d33919 ("Merge pull request #158
> >> >>> >> + from hirooih/clmul-fix-loop-end-condition") of riscv-bitmanip.
> >> >>> >> +
> >> >>> >> + - const: zicbom
> >> >>> >> + description:
> >> >>> >> + The standard Zicbom extension for base cache management operations as
> >> >>> >> + ratified in commit 3dd606f ("Create cmobase-v1.0.pdf") of riscv-CMOs.
> >> >>> >> +
> >> >>> >> + - const: zicbop
> >> >>> >> + description:
> >> >>> >> + The standard Zicbop extension for cache-block prefetch instructions
> >> >>> >> + as ratified in commit 3dd606f ("Create cmobase-v1.0.pdf") of
> >> >>> >> + riscv-CMOs.
> >> >>> >> +
> >> >>> >> + - const: zicboz
> >> >>> >> + description:
> >> >>> >> + The standard Zicboz extension for cache-block zeroing as ratified
> >> >>> >> + in commit 3dd606f ("Create cmobase-v1.0.pdf") of riscv-CMOs.
> >> >>> >> +
> >> >>> >> + - const: zicntr
> >> >>> >> + description:
> >> >>> >> + The standard Zicntr extension for base counters and timers, as
> >> >>> >> + ratified in the 20191213 version of the unprivileged ISA
> >> >>> >> + specification.
> >> >>> >> +
> >> >>> >> + - const: zicsr
> >> >>> >> + description:
> >> >>> >> + The standard Zicsr extension for control and status register
> >> >>> >> + instructions, as ratified in the 20191213 version of the
> >> >>> >> + unprivileged ISA specification.
> >> >>> >> +
> >> >>> >> + - const: zifencei
> >> >>> >> + description:
> >> >>> >> + The standard Zifencei extension for instruction-fetch fence, as
> >> >>> >> + ratified in the 20191213 version of the unprivileged ISA
> >> >>> >> + specification.
> >> >>> >> +
> >> >>> >> + - const: zihintpause
> >> >>> >> + description:
> >> >>> >> + The standard Zihintpause extension for pause hints, as ratified in
> >> >>> >> + commit d8ab5c7 ("Zihintpause is ratified") of the riscv-isa-manual.
> >> >>> >> +
> >> >>> >> + - const: zihpm
> >> >>> >> + description:
> >> >>> >> + The standard Zihpm extension for hardware performance counters, as
> >> >>> >> + ratified in the 20191213 version of the unprivileged ISA
> >> >>> >> + specification.
> >> >>> >> +
> >> >>> >> + - const: ztso
> >> >>> >> + description:
> >> >>> >> + The standard Ztso extension for total store ordering, as ratified
> >> >>> >> + in commit 2e5236 ("Ztso is now ratified.") of the
> >> >>> >> + riscv-isa-manual.
> >> >>> >> +
> >> >>> >> +additionalProperties: true
> >> >>> >> +...
> >> >>> >> --
> >> >>> >> 2.40.1
> >> >>> >>