[PATCH 0/2] riscv,isa fixups

[PATCH 0/2] riscv,isa fixups

[Conor Dooley]

I noticed today while looking at the isa manual that I had not accounted
for another couple of edge cases with my regex. As before, I think
attempting to validate the canonical order for multiletter stuff makes
no sense - but we should totally try to avoid false-positives for
combinations that are known to be valid.

Thanks,
Conor.

CC: Conor Dooley <conor@kernel.org>
CC: Rob Herring <robh+dt@kernel.org>
CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
CC: Paul Walmsley <paul.walmsley@sifive.com>
CC: Palmer Dabbelt <palmer@dabbelt.com>
CC: Albert Ou <aou@eecs.berkeley.edu>
CC: Heiko Stuebner <heiko@sntech.de>
CC: Andrew Jones <ajones@ventanamicro.com>
CC: Guo Ren <guoren@kernel.org>
CC: linux-riscv@lists.infradead.org
CC: devicetree@vger.kernel.org
CC: linux-kernel@vger.kernel.org

Conor Dooley (2):
  dt-bindings: riscv: fix underscore requirement for addtional standard
    extensions
  dt-bindings: riscv: fix single letter canonical order

 Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.38.1


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[PATCH 1/2] dt-bindings: riscv: fix underscore requirement for addtional standard extensions

[Conor Dooley]

The RISC-V ISA Manual allows for the first Additional Standard
Extension having no leading underscore. Only if there are multiple
Additional Standard Extensions is it needed to have an underscore.

The dt-binding does not validate that a multi-letter extension is
canonically ordered, as that'd need an even worse regex than is here,
but it should not fail validation for valid ISA strings.

Allow the first Z multi-letter extension to appear immediately prior
after the single-letter extensions.

Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
index 90a7cabf58fe..e80c967a4fa4 100644
--- a/Documentation/devicetree/bindings/riscv/cpus.yaml
+++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
@@ -80,7 +80,7 @@ properties:
       insensitive, letters in the riscv,isa string must be all
       lowercase to simplify parsing.
     $ref: "/schemas/types.yaml#/definitions/string"
-    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:_[hsxz](?:[a-z])+)*$
+    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
 
   # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
   timebase-frequency: false
-- 
2.38.1


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[PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Conor Dooley]

I used the wikipedia table for ordering extensions when updating the
pattern here in foo.
Unfortunately that table did not match canonical order, as defined by
the RISC-V ISA Manual, which defines extension ordering in (what is
currently) Table 41, "Standard ISA extension names". Fix things up by
re-sorting v (vector) and adding p (packed-simd) & j (dynamic
languages). The e (reduced integer) and g (general) extensions are still
intentionally left out.

Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
index e80c967a4fa4..b7462ea2dbe4 100644
--- a/Documentation/devicetree/bindings/riscv/cpus.yaml
+++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
@@ -80,7 +80,7 @@ properties:
       insensitive, letters in the riscv,isa string must be all
       lowercase to simplify parsing.
     $ref: "/schemas/types.yaml#/definitions/string"
-    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
+    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
 
   # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
   timebase-frequency: false
-- 
2.38.1


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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Heiko Stübner]

Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
> I used the wikipedia table for ordering extensions when updating the
> pattern here in foo.

	    ^ foo? :-)

> Unfortunately that table did not match canonical order, as defined by
> the RISC-V ISA Manual, which defines extension ordering in (what is
> currently) Table 41, "Standard ISA extension names". Fix things up by
> re-sorting v (vector) and adding p (packed-simd) & j (dynamic
> languages). The e (reduced integer) and g (general) extensions are still
> intentionally left out.
> 
> Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
> Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

So I have compared the new pattern to the isa manual,
and it looks like the order checks out, so

Reviewed-by: Heiko Stuebner <heiko@sntech.de>

> ---
>  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> index e80c967a4fa4..b7462ea2dbe4 100644
> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> @@ -80,7 +80,7 @@ properties:
>        insensitive, letters in the riscv,isa string must be all
>        lowercase to simplify parsing.
>      $ref: "/schemas/types.yaml#/definitions/string"
> -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
>  
>    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>    timebase-frequency: false
> 





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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Conor Dooley]

On Thu, Nov 24, 2022 at 02:42:20PM +0100, Heiko Stübner wrote:
> Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
> > I used the wikipedia table for ordering extensions when updating the
> > pattern here in foo.
> 
> 	    ^ foo? :-)

God damn it! I wrote foo, left nvim to check what the fixes tag would
be, came back and added it below but did not update this part of the
commit log...

> > Unfortunately that table did not match canonical order, as defined by
> > the RISC-V ISA Manual, which defines extension ordering in (what is
> > currently) Table 41, "Standard ISA extension names". Fix things up by
> > re-sorting v (vector) and adding p (packed-simd) & j (dynamic
> > languages). The e (reduced integer) and g (general) extensions are still
> > intentionally left out.
> > 
> > Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
> > Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
> > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> 
> So I have compared the new pattern to the isa manual,
> and it looks like the order checks out, so
> 
> Reviewed-by: Heiko Stuebner <heiko@sntech.de>

Thanks!


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Re: [PATCH 1/2] dt-bindings: riscv: fix underscore requirement for addtional standard extensions

[Guo Ren]

On Thu, Nov 24, 2022 at 9:06 PM Conor Dooley <conor.dooley@microchip.com> wrote:
>
> The RISC-V ISA Manual allows for the first Additional Standard
> Extension having no leading underscore. Only if there are multiple
> Additional Standard Extensions is it needed to have an underscore.
>
> The dt-binding does not validate that a multi-letter extension is
> canonically ordered, as that'd need an even worse regex than is here,
> but it should not fail validation for valid ISA strings.
>
> Allow the first Z multi-letter extension to appear immediately prior
> after the single-letter extensions.
>
> Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
> Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> index 90a7cabf58fe..e80c967a4fa4 100644
> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> @@ -80,7 +80,7 @@ properties:
>        insensitive, letters in the riscv,isa string must be all
>        lowercase to simplify parsing.
>      $ref: "/schemas/types.yaml#/definitions/string"
> -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:_[hsxz](?:[a-z])+)*$
> +    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
Acked-by: Guo Ren <guoren@kernel.org>

>
>    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>    timebase-frequency: false
> --
> 2.38.1
>


-- 
Best Regards
 Guo Ren

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Guo Ren]

On Thu, Nov 24, 2022 at 9:06 PM Conor Dooley <conor.dooley@microchip.com> wrote:
>
> I used the wikipedia table for ordering extensions when updating the
> pattern here in foo.
> Unfortunately that table did not match canonical order, as defined by
> the RISC-V ISA Manual, which defines extension ordering in (what is
> currently) Table 41, "Standard ISA extension names". Fix things up by
> re-sorting v (vector) and adding p (packed-simd) & j (dynamic
> languages). The e (reduced integer) and g (general) extensions are still
> intentionally left out.
>
> Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
> Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> index e80c967a4fa4..b7462ea2dbe4 100644
> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> @@ -80,7 +80,7 @@ properties:
>        insensitive, letters in the riscv,isa string must be all
>        lowercase to simplify parsing.
>      $ref: "/schemas/types.yaml#/definitions/string"
> -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
Acked-by: Guo Ren <guoren@kernel.org>

>
>    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>    timebase-frequency: false
> --
> 2.38.1
>


-- 
Best Regards
 Guo Ren

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Palmer Dabbelt]

On Thu, 24 Nov 2022 05:42:20 PST (-0800), heiko@sntech.de wrote:
> Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
>> I used the wikipedia table for ordering extensions when updating the
>> pattern here in foo.
>
> 	    ^ foo? :-)
>
>> Unfortunately that table did not match canonical order, as defined by
>> the RISC-V ISA Manual, which defines extension ordering in (what is
>> currently) Table 41, "Standard ISA extension names". Fix things up by
>> re-sorting v (vector) and adding p (packed-simd) & j (dynamic
>> languages). The e (reduced integer) and g (general) extensions are still
>> intentionally left out.
>>
>> Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
>> Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
>> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>
> So I have compared the new pattern to the isa manual,
> and it looks like the order checks out, so

Which ISA manual?  There have been many mutually incompatible ISA string 
encoding rules, at least one of them was a change to the extension 
ordering.  It's not entirely clear what the right answer is here, as we 
can't really parse ISA strings without also knowing the version of the 
ISA manual we're meant to parse them against.  Maybe we just accept 
everything?

IMO it's time to just stop using the ISA string.  It's not a stable 
interface, trying to treat it as such just leads to headaches.  We 
should just come up with some DT-specific way of encoding whatever HW 
features are in question.  Sure it'll be a bit of work to write that all 
down in the DT bindings, but it's going to be way less work than trying 
to keep around all this ISA string parsing code.

I know I've said the opposite before, but there's just been way too many 
breakages here to assume they're going to stop.

> Reviewed-by: Heiko Stuebner <heiko@sntech.de>
>
>> ---
>>  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
>> index e80c967a4fa4..b7462ea2dbe4 100644
>> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
>> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
>> @@ -80,7 +80,7 @@ properties:
>>        insensitive, letters in the riscv,isa string must be all
>>        lowercase to simplify parsing.
>>      $ref: "/schemas/types.yaml#/definitions/string"
>> -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
>> +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
>>
>>    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>>    timebase-frequency: false
>>

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Conor Dooley]

On Mon, Nov 28, 2022 at 09:41:03AM -0800, Palmer Dabbelt wrote:
> On Thu, 24 Nov 2022 05:42:20 PST (-0800), heiko@sntech.de wrote:
> > Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
> > > I used the wikipedia table for ordering extensions when updating the
> > > pattern here in foo.
> > 
> > 	    ^ foo? :-)
> > 
> > > Unfortunately that table did not match canonical order, as defined by
> > > the RISC-V ISA Manual, which defines extension ordering in (what is
> > > currently) Table 41, "Standard ISA extension names". Fix things up by
> > > re-sorting v (vector) and adding p (packed-simd) & j (dynamic
> > > languages). The e (reduced integer) and g (general) extensions are still
> > > intentionally left out.
> > > 
> > > Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
> > > Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
> > > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > 
> > So I have compared the new pattern to the isa manual,
> > and it looks like the order checks out, so
> 
> Which ISA manual?

For me, isa manual is the above github repo.

> There have been many mutually incompatible ISA string
> encoding rules, at least one of them was a change to the extension ordering.
> It's not entirely clear what the right answer is here, as we can't really
> parse ISA strings without also knowing the version of the ISA manual we're
> meant to parse them against.  Maybe we just accept everything?

I don't think accepting everything is the right thing to do. A minimal
amount of validation is still needed here, but I think we can deprecate
the DT property entirely & make it optional if a new-and-improved way of
encoding the in DT is used.

> IMO it's time to just stop using the ISA string.  It's not a stable
> interface, trying to treat it as such just leads to headaches.  We should
> just come up with some DT-specific way of encoding whatever HW features are
> in question.  Sure it'll be a bit of work to write that all down in the DT
> bindings, but it's going to be way less work than trying to keep around all
> this ISA string parsing code.

I'm a glutton for punishment, I'll try and come up with some sort of
other way to encode this information in DT that requires less parsing
and validation. As I said on IRC, something that more resembles:
if (of_property_wahtever("riscv,isa-foo")) { do_enable_foo() }

> I know I've said the opposite before, but there's just been way too many
> breakages here to assume they're going to stop.

:upside_down_face:

Either way, I think these two patches are worth taking in the mean time.

> > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> > 
> > > ---
> > >  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > index e80c967a4fa4..b7462ea2dbe4 100644
> > > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > @@ -80,7 +80,7 @@ properties:
> > >        insensitive, letters in the riscv,isa string must be all
> > >        lowercase to simplify parsing.
> > >      $ref: "/schemas/types.yaml#/definitions/string"
> > > -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> > > +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> > > 
> > >    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
> > >    timebase-frequency: false
> > > 

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Palmer Dabbelt]

On Mon, 28 Nov 2022 10:08:05 PST (-0800), Conor Dooley wrote:
> On Mon, Nov 28, 2022 at 09:41:03AM -0800, Palmer Dabbelt wrote:
>> On Thu, 24 Nov 2022 05:42:20 PST (-0800), heiko@sntech.de wrote:
>> > Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
>> > > I used the wikipedia table for ordering extensions when updating the
>> > > pattern here in foo.
>> >
>> > 	    ^ foo? :-)
>> >
>> > > Unfortunately that table did not match canonical order, as defined by
>> > > the RISC-V ISA Manual, which defines extension ordering in (what is
>> > > currently) Table 41, "Standard ISA extension names". Fix things up by
>> > > re-sorting v (vector) and adding p (packed-simd) & j (dynamic
>> > > languages). The e (reduced integer) and g (general) extensions are still
>> > > intentionally left out.
>> > >
>> > > Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
>> > > Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
>> > > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>> >
>> > So I have compared the new pattern to the isa manual,
>> > and it looks like the order checks out, so
>>
>> Which ISA manual?
>
> For me, isa manual is the above github repo.

Which commit, though?

>
>> There have been many mutually incompatible ISA string
>> encoding rules, at least one of them was a change to the extension ordering.
>> It's not entirely clear what the right answer is here, as we can't really
>> parse ISA strings without also knowing the version of the ISA manual we're
>> meant to parse them against.  Maybe we just accept everything?
>
> I don't think accepting everything is the right thing to do. A minimal
> amount of validation is still needed here, but I think we can deprecate
> the DT property entirely & make it optional if a new-and-improved way of
> encoding the in DT is used.

Sorry, by "everything" I meant "everything that's even been allowed by 
the ISA manual".  Just accetping anything would be bad ;)

>> IMO it's time to just stop using the ISA string.  It's not a stable
>> interface, trying to treat it as such just leads to headaches.  We should
>> just come up with some DT-specific way of encoding whatever HW features are
>> in question.  Sure it'll be a bit of work to write that all down in the DT
>> bindings, but it's going to be way less work than trying to keep around all
>> this ISA string parsing code.
>
> I'm a glutton for punishment, I'll try and come up with some sort of
> other way to encode this information in DT that requires less parsing
> and validation. As I said on IRC, something that more resembles:
> if (of_property_wahtever("riscv,isa-foo")) { do_enable_foo() }

That seems way simpler to me, thanks!  We'll still need to support 
whatever was here as a legacy format, but at least we won't need to add 
a bunch of new stuff to it -- that's where the parsing starts to get 
really complicated.

FWIW, there's a similar dicussion going on in GCC land right now.

>> I know I've said the opposite before, but there's just been way too many
>> breakages here to assume they're going to stop.
>
> :upside_down_face:
>
> Either way, I think these two patches are worth taking in the mean time.

Yep, just as long as it doesn't break any of the strings that were valid 
according to previous versions of the ISA manual I'm fine with it.

>> > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
>> >
>> > > ---
>> > >  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
>> > >  1 file changed, 1 insertion(+), 1 deletion(-)
>> > >
>> > > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
>> > > index e80c967a4fa4..b7462ea2dbe4 100644
>> > > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
>> > > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
>> > > @@ -80,7 +80,7 @@ properties:
>> > >        insensitive, letters in the riscv,isa string must be all
>> > >        lowercase to simplify parsing.
>> > >      $ref: "/schemas/types.yaml#/definitions/string"
>> > > -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
>> > > +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
>> > >
>> > >    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>> > >    timebase-frequency: false
>> > >

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Conor Dooley]

On Mon, Nov 28, 2022 at 10:12:17AM -0800, Palmer Dabbelt wrote:
> On Mon, 28 Nov 2022 10:08:05 PST (-0800), Conor Dooley wrote:
> > On Mon, Nov 28, 2022 at 09:41:03AM -0800, Palmer Dabbelt wrote:
> > > On Thu, 24 Nov 2022 05:42:20 PST (-0800), heiko@sntech.de wrote:
> > > > Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
> > > > > I used the wikipedia table for ordering extensions when updating the
> > > > > pattern here in foo.
> > > >
> > > > 	    ^ foo? :-)
> > > >
> > > > > Unfortunately that table did not match canonical order, as defined by
> > > > > the RISC-V ISA Manual, which defines extension ordering in (what is
> > > > > currently) Table 41, "Standard ISA extension names". Fix things up by
> > > > > re-sorting v (vector) and adding p (packed-simd) & j (dynamic
> > > > > languages). The e (reduced integer) and g (general) extensions are still
> > > > > intentionally left out.
> > > > >
> > > > > Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
> > > > > Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
> > > > > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > > >
> > > > So I have compared the new pattern to the isa manual,
> > > > and it looks like the order checks out, so
> > > 
> > > Which ISA manual?
> > 
> > For me, isa manual is the above github repo.
> 
> Which commit, though?

mutt won't let me paste a clown face emoticon.

> > > There have been many mutually incompatible ISA string
> > > encoding rules, at least one of them was a change to the extension ordering.
> > > It's not entirely clear what the right answer is here, as we can't really
> > > parse ISA strings without also knowing the version of the ISA manual we're
> > > meant to parse them against.  Maybe we just accept everything?
> > 
> > I don't think accepting everything is the right thing to do. A minimal
> > amount of validation is still needed here, but I think we can deprecate
> > the DT property entirely & make it optional if a new-and-improved way of
> > encoding the in DT is used.
> 
> Sorry, by "everything" I meant "everything that's even been allowed by the
> ISA manual".  Just accetping anything would be bad ;)
> 
> > > IMO it's time to just stop using the ISA string.  It's not a stable
> > > interface, trying to treat it as such just leads to headaches.  We should
> > > just come up with some DT-specific way of encoding whatever HW features are
> > > in question.  Sure it'll be a bit of work to write that all down in the DT
> > > bindings, but it's going to be way less work than trying to keep around all
> > > this ISA string parsing code.
> > 
> > I'm a glutton for punishment, I'll try and come up with some sort of
> > other way to encode this information in DT that requires less parsing
> > and validation. As I said on IRC, something that more resembles:
> > if (of_property_wahtever("riscv,isa-foo")) { do_enable_foo() }
> 
> That seems way simpler to me, thanks!  We'll still need to support whatever
> was here as a legacy format, but at least we won't need to add a bunch of
> new stuff to it -- that's where the parsing starts to get really
> complicated.

Yah, and "deprecated" in dt-schema doesn't actually do anything at the
moment other than let humans know not to use something. Just gonna have
to do some sort of "feature-wise AND" between the existing things we
parse from the isa string & whatever riscv,isa-foo stuff later on.

> FWIW, there's a similar dicussion going on in GCC land right now.
> 
> > > I know I've said the opposite before, but there's just been way too many
> > > breakages here to assume they're going to stop.
> > 
> > :upside_down_face:
> > 
> > Either way, I think these two patches are worth taking in the mean time.
> 
> Yep, just as long as it doesn't break any of the strings that were valid
> according to previous versions of the ISA manual I'm fine with it.

I don't think so. I had been looking around for a supposed order for
where to actually put H, which had been dropped - and the only place I
recall seeing that was Wikipedia - which now seems like an awful
decision since the order there looks kinda off anything I see in dozen
or so spec PDFs I have downloaded. But that's where I got the K & V
ordering from that I now think is wrong (and doesn't match any PDF I
have). The other changes relax rules and add letters so they should be
okay too.

> > > > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> > > >
> > > > > ---
> > > > >  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > > > index e80c967a4fa4..b7462ea2dbe4 100644
> > > > > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > > > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > > > @@ -80,7 +80,7 @@ properties:
> > > > >        insensitive, letters in the riscv,isa string must be all
> > > > >        lowercase to simplify parsing.
> > > > >      $ref: "/schemas/types.yaml#/definitions/string"
> > > > > -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> > > > > +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> > > > >
> > > > >    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
> > > > >    timebase-frequency: false
> > > > >

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Palmer Dabbelt]

On Mon, 28 Nov 2022 11:17:21 PST (-0800), Conor Dooley wrote:
> On Mon, Nov 28, 2022 at 10:12:17AM -0800, Palmer Dabbelt wrote:
>> On Mon, 28 Nov 2022 10:08:05 PST (-0800), Conor Dooley wrote:
>> > On Mon, Nov 28, 2022 at 09:41:03AM -0800, Palmer Dabbelt wrote:
>> > > On Thu, 24 Nov 2022 05:42:20 PST (-0800), heiko@sntech.de wrote:
>> > > > Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
>> > > > > I used the wikipedia table for ordering extensions when updating the
>> > > > > pattern here in foo.
>> > > >
>> > > > 	    ^ foo? :-)
>> > > >
>> > > > > Unfortunately that table did not match canonical order, as defined by
>> > > > > the RISC-V ISA Manual, which defines extension ordering in (what is
>> > > > > currently) Table 41, "Standard ISA extension names". Fix things up by
>> > > > > re-sorting v (vector) and adding p (packed-simd) & j (dynamic
>> > > > > languages). The e (reduced integer) and g (general) extensions are still
>> > > > > intentionally left out.
>> > > > >
>> > > > > Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
>> > > > > Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
>> > > > > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>> > > >
>> > > > So I have compared the new pattern to the isa manual,
>> > > > and it looks like the order checks out, so
>> > >
>> > > Which ISA manual?
>> >
>> > For me, isa manual is the above github repo.
>>
>> Which commit, though?
>
> mutt won't let me paste a clown face emoticon.
>
>> > > There have been many mutually incompatible ISA string
>> > > encoding rules, at least one of them was a change to the extension ordering.
>> > > It's not entirely clear what the right answer is here, as we can't really
>> > > parse ISA strings without also knowing the version of the ISA manual we're
>> > > meant to parse them against.  Maybe we just accept everything?
>> >
>> > I don't think accepting everything is the right thing to do. A minimal
>> > amount of validation is still needed here, but I think we can deprecate
>> > the DT property entirely & make it optional if a new-and-improved way of
>> > encoding the in DT is used.
>>
>> Sorry, by "everything" I meant "everything that's even been allowed by the
>> ISA manual".  Just accetping anything would be bad ;)
>>
>> > > IMO it's time to just stop using the ISA string.  It's not a stable
>> > > interface, trying to treat it as such just leads to headaches.  We should
>> > > just come up with some DT-specific way of encoding whatever HW features are
>> > > in question.  Sure it'll be a bit of work to write that all down in the DT
>> > > bindings, but it's going to be way less work than trying to keep around all
>> > > this ISA string parsing code.
>> >
>> > I'm a glutton for punishment, I'll try and come up with some sort of
>> > other way to encode this information in DT that requires less parsing
>> > and validation. As I said on IRC, something that more resembles:
>> > if (of_property_wahtever("riscv,isa-foo")) { do_enable_foo() }
>>
>> That seems way simpler to me, thanks!  We'll still need to support whatever
>> was here as a legacy format, but at least we won't need to add a bunch of
>> new stuff to it -- that's where the parsing starts to get really
>> complicated.
>
> Yah, and "deprecated" in dt-schema doesn't actually do anything at the
> moment other than let humans know not to use something. Just gonna have
> to do some sort of "feature-wise AND" between the existing things we
> parse from the isa string & whatever riscv,isa-foo stuff later on.

I suppose this is more of a Rob question, but could we just make the DT 
bindings match the current ISA manual's rules and then have the kernel's 
"riscv,isa" string parser accept more orderings to remain compatible?

Sort of a API vs ABI stability question, but for DTB and bindngs.

>> FWIW, there's a similar dicussion going on in GCC land right now.
>>
>> > > I know I've said the opposite before, but there's just been way too many
>> > > breakages here to assume they're going to stop.
>> >
>> > :upside_down_face:
>> >
>> > Either way, I think these two patches are worth taking in the mean time.
>>
>> Yep, just as long as it doesn't break any of the strings that were valid
>> according to previous versions of the ISA manual I'm fine with it.
>
> I don't think so. I had been looking around for a supposed order for
> where to actually put H, which had been dropped - and the only place I
> recall seeing that was Wikipedia - which now seems like an awful
> decision since the order there looks kinda off anything I see in dozen
> or so spec PDFs I have downloaded. But that's where I got the K & V
> ordering from that I now think is wrong (and doesn't match any PDF I
> have). The other changes relax rules and add letters so they should be
> okay too.

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

as it sounds like there aren't even any fixed rules, so I guess none of 
this even matters?

>
>> > > > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
>> > > >
>> > > > > ---
>> > > > >  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
>> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
>> > > > >
>> > > > > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
>> > > > > index e80c967a4fa4..b7462ea2dbe4 100644
>> > > > > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
>> > > > > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
>> > > > > @@ -80,7 +80,7 @@ properties:
>> > > > >        insensitive, letters in the riscv,isa string must be all
>> > > > >        lowercase to simplify parsing.
>> > > > >      $ref: "/schemas/types.yaml#/definitions/string"
>> > > > > -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
>> > > > > +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
>> > > > >
>> > > > >    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
>> > > > >    timebase-frequency: false
>> > > > >

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Andrew Jones]

On Mon, Nov 28, 2022 at 03:41:19PM -0800, Palmer Dabbelt wrote:
> On Mon, 28 Nov 2022 11:17:21 PST (-0800), Conor Dooley wrote:
> > On Mon, Nov 28, 2022 at 10:12:17AM -0800, Palmer Dabbelt wrote:
> > > On Mon, 28 Nov 2022 10:08:05 PST (-0800), Conor Dooley wrote:
> > > > On Mon, Nov 28, 2022 at 09:41:03AM -0800, Palmer Dabbelt wrote:
> > > > > On Thu, 24 Nov 2022 05:42:20 PST (-0800), heiko@sntech.de wrote:
> > > > > > Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
> > > > > > > I used the wikipedia table for ordering extensions when updating the
> > > > > > > pattern here in foo.
> > > > > >
> > > > > > 	    ^ foo? :-)
> > > > > >
> > > > > > > Unfortunately that table did not match canonical order, as defined by
> > > > > > > the RISC-V ISA Manual, which defines extension ordering in (what is
> > > > > > > currently) Table 41, "Standard ISA extension names". Fix things up by
> > > > > > > re-sorting v (vector) and adding p (packed-simd) & j (dynamic
> > > > > > > languages). The e (reduced integer) and g (general) extensions are still
> > > > > > > intentionally left out.
> > > > > > >
> > > > > > > Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
> > > > > > > Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
> > > > > > > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > > > > >
> > > > > > So I have compared the new pattern to the isa manual,
> > > > > > and it looks like the order checks out, so
> > > > >
> > > > > Which ISA manual?
> > > >
> > > > For me, isa manual is the above github repo.
> > > 
> > > Which commit, though?
> > 
> > mutt won't let me paste a clown face emoticon.
> > 
> > > > > There have been many mutually incompatible ISA string
> > > > > encoding rules, at least one of them was a change to the extension ordering.
> > > > > It's not entirely clear what the right answer is here, as we can't really
> > > > > parse ISA strings without also knowing the version of the ISA manual we're
> > > > > meant to parse them against.  Maybe we just accept everything?
> > > >
> > > > I don't think accepting everything is the right thing to do. A minimal
> > > > amount of validation is still needed here, but I think we can deprecate
> > > > the DT property entirely & make it optional if a new-and-improved way of
> > > > encoding the in DT is used.
> > > 
> > > Sorry, by "everything" I meant "everything that's even been allowed by the
> > > ISA manual".  Just accetping anything would be bad ;)
> > > 
> > > > > IMO it's time to just stop using the ISA string.  It's not a stable
> > > > > interface, trying to treat it as such just leads to headaches.  We should
> > > > > just come up with some DT-specific way of encoding whatever HW features are
> > > > > in question.  Sure it'll be a bit of work to write that all down in the DT
> > > > > bindings, but it's going to be way less work than trying to keep around all
> > > > > this ISA string parsing code.
> > > >
> > > > I'm a glutton for punishment, I'll try and come up with some sort of
> > > > other way to encode this information in DT that requires less parsing
> > > > and validation. As I said on IRC, something that more resembles:
> > > > if (of_property_wahtever("riscv,isa-foo")) { do_enable_foo() }
> > > 
> > > That seems way simpler to me, thanks!  We'll still need to support whatever
> > > was here as a legacy format, but at least we won't need to add a bunch of
> > > new stuff to it -- that's where the parsing starts to get really
> > > complicated.

While it's easy for Linux to add new DT nodes when new extension support is
added, it's not so easy to add new ACPI objects. The current plan for ACPI
is to use the ISA string[1]. With that in mind, I think Linux should
continue to parse the string for DT as well.

[1] https://docs.google.com/document/d/1LlCefO_0GQ_7Tf3lzfMPETEfMlGo2FfLRJ09IMqJKEk/edit

> > 
> > Yah, and "deprecated" in dt-schema doesn't actually do anything at the
> > moment other than let humans know not to use something. Just gonna have
> > to do some sort of "feature-wise AND" between the existing things we
> > parse from the isa string & whatever riscv,isa-foo stuff later on.
> 
> I suppose this is more of a Rob question, but could we just make the DT
> bindings match the current ISA manual's rules and then have the kernel's
> "riscv,isa" string parser accept more orderings to remain compatible?
> 
> Sort of a API vs ABI stability question, but for DTB and bindngs.
> 
> > > FWIW, there's a similar dicussion going on in GCC land right now.
> > > 
> > > > > I know I've said the opposite before, but there's just been way too many
> > > > > breakages here to assume they're going to stop.
> > > >
> > > > :upside_down_face:
> > > >
> > > > Either way, I think these two patches are worth taking in the mean time.
> > > 
> > > Yep, just as long as it doesn't break any of the strings that were valid
> > > according to previous versions of the ISA manual I'm fine with it.
> > 
> > I don't think so. I had been looking around for a supposed order for
> > where to actually put H, which had been dropped - and the only place I
> > recall seeing that was Wikipedia - which now seems like an awful
> > decision since the order there looks kinda off anything I see in dozen
> > or so spec PDFs I have downloaded. But that's where I got the K & V
> > ordering from that I now think is wrong (and doesn't match any PDF I
> > have). The other changes relax rules and add letters so they should be
> > okay too.
> 
> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> 
> as it sounds like there aren't even any fixed rules, so I guess none of this
> even matters?

IMHO, we should try to get the spec changed to say that the only order
which matters is that single letter extensions come first (in any order)
and then multi-letter extensions come after (in any order). Parsing
becomes simple and we can publish the string in proc in any order too,
maybe preferring alphabetical order for neatness.

Thanks,
drew

> 
> > 
> > > > > > Reviewed-by: Heiko Stuebner <heiko@sntech.de>
> > > > > >
> > > > > > > ---
> > > > > > >  Documentation/devicetree/bindings/riscv/cpus.yaml | 2 +-
> > > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > > > > > index e80c967a4fa4..b7462ea2dbe4 100644
> > > > > > > --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > > > > > +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> > > > > > > @@ -80,7 +80,7 @@ properties:
> > > > > > >        insensitive, letters in the riscv,isa string must be all
> > > > > > >        lowercase to simplify parsing.
> > > > > > >      $ref: "/schemas/types.yaml#/definitions/string"
> > > > > > > -    pattern: ^rv(?:64|32)imaf?d?q?c?b?v?k?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> > > > > > > +    pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:z(?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$
> > > > > > >
> > > > > > >    # RISC-V requires 'timebase-frequency' in /cpus, so disallow it here
> > > > > > >    timebase-frequency: false
> > > > > > >

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Re: [PATCH 2/2] dt-bindings: riscv: fix single letter canonical order

[Conor Dooley]

Yo Drew, Palmer,

(preserving the conversation in case any DT folks want to chime
in on the ABI comment)

On 29/11/2022 05:19, Andrew Jones wrote:
> On Mon, Nov 28, 2022 at 03:41:19PM -0800, Palmer Dabbelt wrote:
>> On Mon, 28 Nov 2022 11:17:21 PST (-0800), Conor Dooley wrote:
>>> On Mon, Nov 28, 2022 at 10:12:17AM -0800, Palmer Dabbelt wrote:
>>>> On Mon, 28 Nov 2022 10:08:05 PST (-0800), Conor Dooley wrote:
>>>>> On Mon, Nov 28, 2022 at 09:41:03AM -0800, Palmer Dabbelt wrote:
>>>>>> On Thu, 24 Nov 2022 05:42:20 PST (-0800), heiko@sntech.de wrote:
>>>>>>> Am Donnerstag, 24. November 2022, 14:04:41 CET schrieb Conor Dooley:
>>>>>>>> I used the wikipedia table for ordering extensions when updating the
>>>>>>>> pattern here in foo.
>>>>>>>
>>>>>>>          ^ foo? :-)
>>>>>>>
>>>>>>>> Unfortunately that table did not match canonical order, as defined by
>>>>>>>> the RISC-V ISA Manual, which defines extension ordering in (what is
>>>>>>>> currently) Table 41, "Standard ISA extension names". Fix things up by
>>>>>>>> re-sorting v (vector) and adding p (packed-simd) & j (dynamic
>>>>>>>> languages). The e (reduced integer) and g (general) extensions are still
>>>>>>>> intentionally left out.
>>>>>>>>
>>>>>>>> Link: https://github.com/riscv/riscv-isa-manual/releases/tag/riscv-unpriv-pdf-from-asciidoc-15112022 # Chapter 29.5
>>>>>>>> Fixes: 299824e68bd0 ("dt-bindings: riscv: add new riscv,isa strings for emulators")
>>>>>>>> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>>>>>>>
>>>>>>> So I have compared the new pattern to the isa manual,
>>>>>>> and it looks like the order checks out, so
>>>>>>
>>>>>> Which ISA manual?
>>>>>
>>>>> For me, isa manual is the above github repo.
>>>>
>>>> Which commit, though?
>>>
>>> mutt won't let me paste a clown face emoticon.
>>>
>>>>>> There have been many mutually incompatible ISA string
>>>>>> encoding rules, at least one of them was a change to the extension ordering.
>>>>>> It's not entirely clear what the right answer is here, as we can't really
>>>>>> parse ISA strings without also knowing the version of the ISA manual we're
>>>>>> meant to parse them against.  Maybe we just accept everything?
>>>>>
>>>>> I don't think accepting everything is the right thing to do. A minimal
>>>>> amount of validation is still needed here, but I think we can deprecate
>>>>> the DT property entirely & make it optional if a new-and-improved way of
>>>>> encoding the in DT is used.
>>>>
>>>> Sorry, by "everything" I meant "everything that's even been allowed by the
>>>> ISA manual".  Just accetping anything would be bad ;)

I agree. I can always relax the regex if something comes to light - but
it's already pretty forgiving about the ordering of stuff - especially
the multiletter extensions.

>>>>
>>>>>> IMO it's time to just stop using the ISA string.  It's not a stable
>>>>>> interface, trying to treat it as such just leads to headaches.  We should
>>>>>> just come up with some DT-specific way of encoding whatever HW features are
>>>>>> in question.  Sure it'll be a bit of work to write that all down in the DT
>>>>>> bindings, but it's going to be way less work than trying to keep around all
>>>>>> this ISA string parsing code.
>>>>>
>>>>> I'm a glutton for punishment, I'll try and come up with some sort of
>>>>> other way to encode this information in DT that requires less parsing
>>>>> and validation. As I said on IRC, something that more resembles:
>>>>> if (of_property_wahtever("riscv,isa-foo")) { do_enable_foo() }
>>>>
>>>> That seems way simpler to me, thanks!  We'll still need to support whatever
>>>> was here as a legacy format, but at least we won't need to add a bunch of
>>>> new stuff to it -- that's where the parsing starts to get really
>>>> complicated.
> 
> While it's easy for Linux to add new DT nodes when new extension support is
> added, it's not so easy to add new ACPI objects. The current plan for ACPI
> is to use the ISA string[1]. With that in mind, I think Linux should
> continue to parse the string for DT as well.

I was thinking about how to implement this at the gym this morning,
before even reading this mail, and I have gotten cold feet about doing
riscv,isa-foo stuff anyway.

I don't really want to create a confusing, two-location way of turning
features on. We would be either forcing all other operating systems to
switch away from using riscv,isa too or creating a difference between
how Linux handles things compared to, say, FreeBSD or U-Boot.
IOW, if the "v" in riscv,isa turned it on for FreeBSD and a boolean DT
property of riscv,isa-v did it for Linux. I really dislike the idea of
that...

If we are going to have to parse it *anyway* for ACPI, then I think
there's little merit unfortunately.

I think we would also end up ballooning the code with a bunch of checks
for the different extensions which I am not keen on either.
Completely relaxing any parsing rules, as discussed below, seems like
a less user-hostile & more "application" independent way of proceeding.

> [1] https://docs.google.com/document/d/1LlCefO_0GQ_7Tf3lzfMPETEfMlGo2FfLRJ09IMqJKEk/edit
> 
>>>
>>> Yah, and "deprecated" in dt-schema doesn't actually do anything at the
>>> moment other than let humans know not to use something. Just gonna have
>>> to do some sort of "feature-wise AND" between the existing things we

That should be s/AND/OR/

>>> parse from the isa string & whatever riscv,isa-foo stuff later on.
>>
>> I suppose this is more of a Rob question, but could we just make the DT
>> bindings match the current ISA manual's rules and then have the kernel's
>> "riscv,isa" string parser accept more orderings to remain compatible?
>>
>> Sort of a API vs ABI stability question, but for DTB and bindngs.

AFAIU, the kernel needs to keep supporting only what was ever in a
dt-binding to satisfy the DT ABI and our current regex is compatible
with that so that's fine.
Whether or not we have laxer rules within the kernel is fine, as long
as we support whatever we specified previously in the binding.

>>>> FWIW, there's a similar dicussion going on in GCC land right now.
>>>>
>>>>>> I know I've said the opposite before, but there's just been way too many
>>>>>> breakages here to assume they're going to stop.
>>>>>
>>>>> :upside_down_face:
>>>>>
>>>>> Either way, I think these two patches are worth taking in the mean time.
>>>>
>>>> Yep, just as long as it doesn't break any of the strings that were valid
>>>> according to previous versions of the ISA manual I'm fine with it.
>>>
>>> I don't think so. I had been looking around for a supposed order for
>>> where to actually put H, which had been dropped - and the only place I
>>> recall seeing that was Wikipedia - which now seems like an awful
>>> decision since the order there looks kinda off anything I see in dozen
>>> or so spec PDFs I have downloaded. But that's where I got the K & V
>>> ordering from that I now think is wrong (and doesn't match any PDF I
>>> have). The other changes relax rules and add letters so they should be
>>> okay too.
>>
>> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
>> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

I am assuming that w/ these tags I can take this with other DT stuff,
since they're kinda unrelated to the ongoing conversation.

>> as it sounds like there aren't even any fixed rules, so I guess none of this
>> even matters?
> 
> IMHO, we should try to get the spec changed to say that the only order
> which matters is that single letter extensions come first (in any order)

Good luck, I'll +1 your PR.

> and then multi-letter extensions come after (in any order). Parsing
> becomes simple and we can publish the string in proc in any order too,
> maybe preferring alphabetical order for neatness.

Devil's advocate, then we break someone's parser that relied expects
things to be how they were ordered by a prior version of the spec?

Either way, I am happy to vote for a world in which the stuff we put
into /proc follows the loosest possible wording that has ever been
using in the spec (and in fact, I think we *need* to do that).

Per the thread on the Zbb stuff, the table claims it "defines the
canonical order in which extension names must appear in the name
string, with top-to-bottom in table indicating first-to-last in the
name string, e.g., RV32IMACV is legal, whereas RV32IMAVC is not." 

It does not contain an entry for Zihintpause & I cannot see anywhere
in the current incarnation* of the naming.tex document that tells us
how to sort unmentioned Standard Additional Extensions - just that
"Standard supervisor-level extensions should be listed after standard
unprivileged extensions" & "Standard machine-level extensions should
be listed after standard lesser-privileged extensions"

(as an aside, I think that second quote is missing a comma after
standard)

The implication there, is that something like Zihintpause could, per
this version of the spec*, be placed anywhere in the string once the
"Base Integer ISA" constraint is satisfied (or not permitted in the
string at all?). Have I missed something? This particular situation
has been the cause of all of my confusion lately - the doc says it
defines the order by the table, which then has no generic entry for
"Additional Standard Extensions".

* 10eea63205f371ed649355f4cf7a80716335958f

Anyways, I feel hopelessly confused by all of this stuff & I wish
we could just write down exactly what *we* are doing w.r.t. internal
kernel representation (yeah yeah https://xkcd.com/927/) as absolutely
noone seems to be sure what to do. Maybe in the "patch acceptance"
document.

In terms of our own parsing of the isa string, assuming single-letter
followed by multiletter is about the only assumption that I think we
should be making.
I don't think that parsing in any order after that really becomes an
issue unless we have x depends on y sort of things where x is not
explicitly required.

The specs currently say:
"Some ISA extensions depend on the presence of other extensions, e.g.,
``D'' depends on ``F'' and ``F'' depends on ``Zicsr''.  These
dependences may be implicit in the ISA name: for example, RV32IF is
equivalent to RV32IFZicsr, and RV32ID is equivalent to RV32IFD and
RV32IFDZicsr."

That'd mean that out-of-canonical-order processing isn't too bad since
the more expansive extension would imply the others too.
Who knows if that will hold for future extensions, but maybe we can
deal with things down the road.

I'll take a look at the current parser to at least get things
straightened out in my own head and then maybe submit a patch for the
docs as mentioned above so we can at least point patch submitters
at something concrete?

I am really sorry for all of the "chaos" that I've sown over the last
few days on this sort of subject, but everyone is doing different things
and it triggers my OCD heh. Knowing where we stand would be nice :)

Thanks,
Conor.


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[RFC 0/2] Putting some basic order on isa extension stuff

[Conor Dooley]

RFC:
- I have not even tested this, I just did an allmodconfig
- I don't know if I re-ordered something that is sacrosanct
- I don't know if I changed all of the instances
- I didn't write a proper commit message for "patch" 2/2

With those caveats out of the way - all I did here was try to make
things consistent so that it'd be easier to point patch submitters at a
"do this order please".

I never know which of these can be moved without breaking stuff - but
they all seem to be internal use stuff since they're not in uapi?

@drew, I didn't touch the KVM ones - are they re-sortable too? My base
here is rc7 so if you did a reorder at any point there I'd not see it ;)

CC: conor.dooley@microchip.com
CC: ajones@ventanamicro.com
CC: aou@eecs.berkeley.edu
CC: conor@kernel.org
CC: devicetree@vger.kernel.org
CC: guoren@kernel.org
CC: heiko@sntech.de
CC: krzysztof.kozlowski+dt@linaro.org
CC: linux-kernel@vger.kernel.org
CC: linux-riscv@lists.infradead.org
CC: palmer@dabbelt.com
CC: paul.walmsley@sifive.com
CC: robh+dt@kernel.org

Conor Dooley (2):
  RISC-V: clarify ISA string ordering rules in cpu.c
  RISC-V: resort all extensions in "canonical" order

 arch/riscv/include/asm/hwcap.h |  6 +++---
 arch/riscv/kernel/cpu.c        | 26 +++++++++++++++++++-------
 arch/riscv/kernel/cpufeature.c |  4 ++--
 3 files changed, 24 insertions(+), 12 deletions(-)

-- 
2.38.1


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[RFC 1/2] RISC-V: clarify ISA string ordering rules in cpu.c

[Conor Dooley]

While the list of rules may have been accurate when created, it now
lacks some clarity in the face of isa-manual updates. Specifically:

- there is no mention here of a distinction between regular 'Z'
  extensions which are "Additional Standard Extensions" and "Zxm"
  extensions which are "Standard Machine-Level Extensions"

- there is also no explicit mention of where either should be sorted in
  the list

- underscores are only required between two *multi-letter* extensions but
  the list of rules implies that this is required between a multi-letter
  extension and any other extension. IOW "rv64imafdzicsr_zifencei" is a
  valid string

Attempt to clean up the list of rules, by adding information on the
above & sprinkling in some white space for readability.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/kernel/cpu.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 852ecccd8920..5e42c92a8456 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -120,20 +120,32 @@ device_initcall(riscv_cpuinfo_init);
 		.uprop = #UPROP,				\
 		.isa_ext_id = EXTID,				\
 	}
+
 /*
  * Here are the ordering rules of extension naming defined by RISC-V
  * specification :
- * 1. All extensions should be separated from other multi-letter extensions
- *    by an underscore.
+ *
+ * 1. All multi-letter extensions should be separated from other multi-letter
+ *    extensions by an underscore.
+ *
  * 2. The first letter following the 'Z' conventionally indicates the most
  *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
- *    If multiple 'Z' extensions are named, they should be ordered first
- *    by category, then alphabetically within a category.
+ *    'Z' extensions should be sorted after single-letter extensions and before
+ *    any higher-privileged extensions.
+ *    If multiple 'Z' extensions are named, they should be ordered first by
+ *    category, then alphabetically within a category.
+ *
  * 3. Standard supervisor-level extensions (starts with 'S') should be
  *    listed after standard unprivileged extensions.  If multiple
  *    supervisor-level extensions are listed, they should be ordered
  *    alphabetically.
- * 4. Non-standard extensions (starts with 'X') must be listed after all
+ *
+ * 4  Standard machine-level extensions (starts with 'Zxm') should be
+ *    listed after any lower-privileged, standard extensions.  If multiple
+ *    machine-level extensions are listed, they should be ordered
+ *    alphabetically.
+ *
+ * 5. Non-standard extensions (starts with 'X') must be listed after all
  *    standard extensions. They must be separated from other multi-letter
  *    extensions by an underscore.
  */
-- 
2.38.1


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[RFC 2/2] RISC-V: resort all extensions in "canonical" order

[Conor Dooley]

Per the comment in cpu.c, re-sort all lists/tables/enums/whatever in
arch/riscv (apart from KVM) in the current edition of what the isa
manual considers to be "canonical" order.

None of this is in uapi, so we are free to re-order it? I'm never sure
when it comes to hwcap...

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/include/asm/hwcap.h | 6 +++---
 arch/riscv/kernel/cpu.c        | 4 ++--
 arch/riscv/kernel/cpufeature.c | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index b22525290073..d7d5f27619ee 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -53,12 +53,12 @@ extern unsigned long elf_hwcap;
  * available logical extension id.
  */
 enum riscv_isa_ext_id {
-	RISCV_ISA_EXT_SSCOFPMF = RISCV_ISA_EXT_BASE,
-	RISCV_ISA_EXT_SVPBMT,
-	RISCV_ISA_EXT_ZICBOM,
+	RISCV_ISA_EXT_ZICBOM = RISCV_ISA_EXT_BASE,
 	RISCV_ISA_EXT_ZIHINTPAUSE,
+	RISCV_ISA_EXT_SSCOFPMF,
 	RISCV_ISA_EXT_SSTC,
 	RISCV_ISA_EXT_SVINVAL,
+	RISCV_ISA_EXT_SVPBMT,
 	RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX,
 };
 
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 5e42c92a8456..1d0fa0ebf6a8 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -150,12 +150,12 @@ device_initcall(riscv_cpuinfo_init);
  *    extensions by an underscore.
  */
 static struct riscv_isa_ext_data isa_ext_arr[] = {
+	__RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
+	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
 	__RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
 	__RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),
 	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
 	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
-	__RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
-	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
 	__RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
 };
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 694267d1fe81..d3df72c4b94f 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -199,12 +199,12 @@ void __init riscv_fill_hwcap(void)
 				this_hwcap |= isa2hwcap[(unsigned char)(*ext)];
 				set_bit(*ext - 'a', this_isa);
 			} else {
-				SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF);
-				SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);
 				SET_ISA_EXT_MAP("zicbom", RISCV_ISA_EXT_ZICBOM);
 				SET_ISA_EXT_MAP("zihintpause", RISCV_ISA_EXT_ZIHINTPAUSE);
+				SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF);
 				SET_ISA_EXT_MAP("sstc", RISCV_ISA_EXT_SSTC);
 				SET_ISA_EXT_MAP("svinval", RISCV_ISA_EXT_SVINVAL);
+				SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);
 			}
 #undef SET_ISA_EXT_MAP
 		}
-- 
2.38.1


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Re: [RFC 0/2] Putting some basic order on isa extension stuff

[Andrew Jones]

On Tue, Nov 29, 2022 at 02:47:41PM +0000, Conor Dooley wrote:
> RFC:
> - I have not even tested this, I just did an allmodconfig
> - I don't know if I re-ordered something that is sacrosanct
> - I don't know if I changed all of the instances
> - I didn't write a proper commit message for "patch" 2/2
> 
> With those caveats out of the way - all I did here was try to make
> things consistent so that it'd be easier to point patch submitters at a
> "do this order please".
> 
> I never know which of these can be moved without breaking stuff - but
> they all seem to be internal use stuff since they're not in uapi?
> 
> @drew, I didn't touch the KVM ones - are they re-sortable too? My base
> here is rc7 so if you did a reorder at any point there I'd not see it ;)

Right, we can't touch enum KVM_RISCV_ISA_EXT_ID as that's UAPI. All new
extensions must be added at the bottom. We originally also had to keep
kvm_isa_ext_arr[] in that order, but commit 1b5cbb8733f9 ("RISC-V: KVM:
Make ISA ext mappings explicit") allows us to list its elements in any
order, which means we could sort them in canonical order, if we wanted
to. I think I'd rather have them in alphabetical order, though (they
nearly are at the moment, except for the bottom two...) The only other
place we have ISA extensions listed in KVM is in a switch statement,
which of course doesn't matter, and it's currently in alphabetical order.

Thanks,
drew

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Re: [RFC 1/2] RISC-V: clarify ISA string ordering rules in cpu.c

[Andrew Jones]

On Tue, Nov 29, 2022 at 02:47:42PM +0000, Conor Dooley wrote:
> While the list of rules may have been accurate when created, it now
> lacks some clarity in the face of isa-manual updates. Specifically:
> 
> - there is no mention here of a distinction between regular 'Z'
>   extensions which are "Additional Standard Extensions" and "Zxm"
>   extensions which are "Standard Machine-Level Extensions"
> 
> - there is also no explicit mention of where either should be sorted in
>   the list
> 
> - underscores are only required between two *multi-letter* extensions but
>   the list of rules implies that this is required between a multi-letter
>   extension and any other extension. IOW "rv64imafdzicsr_zifencei" is a
>   valid string
> 
> Attempt to clean up the list of rules, by adding information on the
> above & sprinkling in some white space for readability.
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  arch/riscv/kernel/cpu.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 852ecccd8920..5e42c92a8456 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -120,20 +120,32 @@ device_initcall(riscv_cpuinfo_init);
>  		.uprop = #UPROP,				\
>  		.isa_ext_id = EXTID,				\
>  	}
> +
>  /*
>   * Here are the ordering rules of extension naming defined by RISC-V
>   * specification :
> - * 1. All extensions should be separated from other multi-letter extensions
> - *    by an underscore.
> + *
> + * 1. All multi-letter extensions should be separated from other multi-letter
> + *    extensions by an underscore.
> + *
>   * 2. The first letter following the 'Z' conventionally indicates the most
>   *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
> - *    If multiple 'Z' extensions are named, they should be ordered first
> - *    by category, then alphabetically within a category.
> + *    'Z' extensions should be sorted after single-letter extensions and before
> + *    any higher-privileged extensions.
> + *    If multiple 'Z' extensions are named, they should be ordered first by
> + *    category, then alphabetically within a category.
> + *
>   * 3. Standard supervisor-level extensions (starts with 'S') should be
>   *    listed after standard unprivileged extensions.  If multiple
>   *    supervisor-level extensions are listed, they should be ordered
>   *    alphabetically.
> - * 4. Non-standard extensions (starts with 'X') must be listed after all
> + *
> + * 4  Standard machine-level extensions (starts with 'Zxm') should be
> + *    listed after any lower-privileged, standard extensions.  If multiple
> + *    machine-level extensions are listed, they should be ordered
> + *    alphabetically.
> + *
> + * 5. Non-standard extensions (starts with 'X') must be listed after all
>   *    standard extensions. They must be separated from other multi-letter
>   *    extensions by an underscore.
>   */
> -- 
> 2.38.1
>

Alternatively, we could change the comment to just point out the spec
chapter and provide an example, e.g.

/*
 * The canonical order of ISA extension names in the ISA string is defined in
 * chapter 27 of the unprivileged spec. An example string following the
 * order is
 *
 *   rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux
 *
 * Notice how Z-extensions are first sorted by category using the canonical
 * order of the first letter following the Z. Extension groups are in the
 * order specified in chapter 27. Extensions within each group are sorted
 * alphabetically.
 */


Thanks,
drew

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Re: [RFC 2/2] RISC-V: resort all extensions in "canonical" order

[Andrew Jones]

On Tue, Nov 29, 2022 at 02:47:43PM +0000, Conor Dooley wrote:
> Per the comment in cpu.c, re-sort all lists/tables/enums/whatever in
> arch/riscv (apart from KVM) in the current edition of what the isa
> manual considers to be "canonical" order.
> 
> None of this is in uapi, so we are free to re-order it? I'm never sure
> when it comes to hwcap...
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>  arch/riscv/include/asm/hwcap.h | 6 +++---
>  arch/riscv/kernel/cpu.c        | 4 ++--
>  arch/riscv/kernel/cpufeature.c | 4 ++--
>  3 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index b22525290073..d7d5f27619ee 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -53,12 +53,12 @@ extern unsigned long elf_hwcap;
>   * available logical extension id.
>   */
>  enum riscv_isa_ext_id {
> -	RISCV_ISA_EXT_SSCOFPMF = RISCV_ISA_EXT_BASE,
> -	RISCV_ISA_EXT_SVPBMT,
> -	RISCV_ISA_EXT_ZICBOM,
> +	RISCV_ISA_EXT_ZICBOM = RISCV_ISA_EXT_BASE,
>  	RISCV_ISA_EXT_ZIHINTPAUSE,
> +	RISCV_ISA_EXT_SSCOFPMF,
>  	RISCV_ISA_EXT_SSTC,
>  	RISCV_ISA_EXT_SVINVAL,
> +	RISCV_ISA_EXT_SVPBMT,
>  	RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX,

Or,

@@ -48,17 +48,16 @@ extern unsigned long elf_hwcap;
 /*
  * This enum represent the logical ID for each multi-letter RISC-V ISA extension.
  * The logical ID should start from RISCV_ISA_EXT_BASE and must not exceed
- * RISCV_ISA_EXT_MAX. 0-25 range is reserved for single letter
- * extensions while all the multi-letter extensions should define the next
- * available logical extension id.
+ * RISCV_ISA_EXT_MAX. While the order doesn't matter, we keep it sorted
+ * alphabetically for neatness.
  */
 enum riscv_isa_ext_id {
        RISCV_ISA_EXT_SSCOFPMF = RISCV_ISA_EXT_BASE,
+       RISCV_ISA_EXT_SSTC,
+       RISCV_ISA_EXT_SVINVAL,
        RISCV_ISA_EXT_SVPBMT,
        RISCV_ISA_EXT_ZICBOM,
        RISCV_ISA_EXT_ZIHINTPAUSE,
-       RISCV_ISA_EXT_SSTC,
-       RISCV_ISA_EXT_SVINVAL,
        RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX,
 };


>  };
>  
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 5e42c92a8456..1d0fa0ebf6a8 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -150,12 +150,12 @@ device_initcall(riscv_cpuinfo_init);
>   *    extensions by an underscore.
>   */
>  static struct riscv_isa_ext_data isa_ext_arr[] = {
> +	__RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
> +	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
>  	__RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
>  	__RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),
>  	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
>  	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
> -	__RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
> -	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
>  	__RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
>  };

Yes, this one should be put in canonical order (I guess).

>  
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 694267d1fe81..d3df72c4b94f 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -199,12 +199,12 @@ void __init riscv_fill_hwcap(void)
>  				this_hwcap |= isa2hwcap[(unsigned char)(*ext)];
>  				set_bit(*ext - 'a', this_isa);
>  			} else {
> -				SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF);
> -				SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);
>  				SET_ISA_EXT_MAP("zicbom", RISCV_ISA_EXT_ZICBOM);
>  				SET_ISA_EXT_MAP("zihintpause", RISCV_ISA_EXT_ZIHINTPAUSE);
> +				SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF);
>  				SET_ISA_EXT_MAP("sstc", RISCV_ISA_EXT_SSTC);
>  				SET_ISA_EXT_MAP("svinval", RISCV_ISA_EXT_SVINVAL);
> +				SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);

Or,

@@ -199,12 +199,16 @@ void __init riscv_fill_hwcap(void)
                                this_hwcap |= isa2hwcap[(unsigned char)(*ext)];
                                set_bit(*ext - 'a', this_isa);
                        } else {
+                               /*
+                                * While the order doesn't matter here, we sort
+                                * alphabetically for neatness.
+                                */
                                SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF);
+                               SET_ISA_EXT_MAP("sstc", RISCV_ISA_EXT_SSTC);
+                               SET_ISA_EXT_MAP("svinval", RISCV_ISA_EXT_SVINVAL);
                                SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);
                                SET_ISA_EXT_MAP("zicbom", RISCV_ISA_EXT_ZICBOM);
                                SET_ISA_EXT_MAP("zihintpause", RISCV_ISA_EXT_ZIHINTPAUSE);
-                               SET_ISA_EXT_MAP("sstc", RISCV_ISA_EXT_SSTC);
-                               SET_ISA_EXT_MAP("svinval", RISCV_ISA_EXT_SVINVAL);
                        }
 #undef SET_ISA_EXT_MAP
                }

>  			}
>  #undef SET_ISA_EXT_MAP
>  		}
> -- 
> 2.38.1
>

Thanks,
drew

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Re: [RFC 0/2] Putting some basic order on isa extension stuff

[Conor Dooley]

On Tue, Nov 29, 2022 at 04:48:32PM +0100, Andrew Jones wrote:
> On Tue, Nov 29, 2022 at 02:47:41PM +0000, Conor Dooley wrote:
> > RFC:
> > - I have not even tested this, I just did an allmodconfig
> > - I don't know if I re-ordered something that is sacrosanct
> > - I don't know if I changed all of the instances
> > - I didn't write a proper commit message for "patch" 2/2
> > 
> > With those caveats out of the way - all I did here was try to make
> > things consistent so that it'd be easier to point patch submitters at a
> > "do this order please".
> > 
> > I never know which of these can be moved without breaking stuff - but
> > they all seem to be internal use stuff since they're not in uapi?
> > 
> > @drew, I didn't touch the KVM ones - are they re-sortable too? My base
> > here is rc7 so if you did a reorder at any point there I'd not see it ;)
> 
> Right, we can't touch enum KVM_RISCV_ISA_EXT_ID as that's UAPI. All new
> extensions must be added at the bottom. We originally also had to keep
> kvm_isa_ext_arr[] in that order, but commit 1b5cbb8733f9 ("RISC-V: KVM:

Right, I knew that something had been changed in KVM land. It's probably
a good idea to say sort them all alphabetically apart from whichever
ones must be in other orders & explicitly note the reasons in-place.

> Make ISA ext mappings explicit") allows us to list its elements in any
> order, which means we could sort them in canonical order, if we wanted
> to. I think I'd rather have them in alphabetical order, though (they
> nearly are at the moment, except for the bottom two...) The only other
> place we have ISA extensions listed in KVM is in a switch statement,
> which of course doesn't matter, and it's currently in alphabetical order.

I did see the one in uAPI for KVM. Your idea in 2/2 of doing
alphabetical unless otherwise stated works for me as I just want
something concrete! If it works for the chief too, I'll resubmit and
drop the RFC...


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Re: [RFC 1/2] RISC-V: clarify ISA string ordering rules in cpu.c

[Conor Dooley]

On Tue, Nov 29, 2022 at 05:12:23PM +0100, Andrew Jones wrote:
> On Tue, Nov 29, 2022 at 02:47:42PM +0000, Conor Dooley wrote:
> > While the list of rules may have been accurate when created, it now
> > lacks some clarity in the face of isa-manual updates. Specifically:
> > 
> > - there is no mention here of a distinction between regular 'Z'
> >   extensions which are "Additional Standard Extensions" and "Zxm"
> >   extensions which are "Standard Machine-Level Extensions"
> > 
> > - there is also no explicit mention of where either should be sorted in
> >   the list
> > 
> > - underscores are only required between two *multi-letter* extensions but
> >   the list of rules implies that this is required between a multi-letter
> >   extension and any other extension. IOW "rv64imafdzicsr_zifencei" is a
> >   valid string
> > 
> > Attempt to clean up the list of rules, by adding information on the
> > above & sprinkling in some white space for readability.
> > 
> > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > ---
> >  arch/riscv/kernel/cpu.c | 22 +++++++++++++++++-----
> >  1 file changed, 17 insertions(+), 5 deletions(-)
> > 
> > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> > index 852ecccd8920..5e42c92a8456 100644
> > --- a/arch/riscv/kernel/cpu.c
> > +++ b/arch/riscv/kernel/cpu.c
> > @@ -120,20 +120,32 @@ device_initcall(riscv_cpuinfo_init);
> >  		.uprop = #UPROP,				\
> >  		.isa_ext_id = EXTID,				\
> >  	}
> > +
> >  /*
> >   * Here are the ordering rules of extension naming defined by RISC-V
> >   * specification :
> > - * 1. All extensions should be separated from other multi-letter extensions
> > - *    by an underscore.
> > + *
> > + * 1. All multi-letter extensions should be separated from other multi-letter
> > + *    extensions by an underscore.
> > + *
> >   * 2. The first letter following the 'Z' conventionally indicates the most
> >   *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
> > - *    If multiple 'Z' extensions are named, they should be ordered first
> > - *    by category, then alphabetically within a category.
> > + *    'Z' extensions should be sorted after single-letter extensions and before
> > + *    any higher-privileged extensions.
> > + *    If multiple 'Z' extensions are named, they should be ordered first by
> > + *    category, then alphabetically within a category.
> > + *
> >   * 3. Standard supervisor-level extensions (starts with 'S') should be
> >   *    listed after standard unprivileged extensions.  If multiple
> >   *    supervisor-level extensions are listed, they should be ordered
> >   *    alphabetically.
> > - * 4. Non-standard extensions (starts with 'X') must be listed after all
> > + *
> > + * 4  Standard machine-level extensions (starts with 'Zxm') should be
> > + *    listed after any lower-privileged, standard extensions.  If multiple
> > + *    machine-level extensions are listed, they should be ordered
> > + *    alphabetically.
> > + *
> > + * 5. Non-standard extensions (starts with 'X') must be listed after all
> >   *    standard extensions. They must be separated from other multi-letter
> >   *    extensions by an underscore.
> >   */
> > -- 
> > 2.38.1
> >
> 
> Alternatively, we could change the comment to just point out the spec
> chapter and provide an example, e.g.

IDK, maybe add the reference & the example but keep the summary?

> /*
>  * The canonical order of ISA extension names in the ISA string is defined in
>  * chapter 27 of the unprivileged spec. An example string following the
>  * order is
>  *
>  *   rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux
>  *
>  * Notice how Z-extensions are first sorted by category using the canonical
>  * order of the first letter following the Z. Extension groups are in the
>  * order specified in chapter 27. Extensions within each group are sorted
>  * alphabetically.
>  */
> 
> 
> Thanks,
> drew

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Re: [RFC 1/2] RISC-V: clarify ISA string ordering rules in cpu.c

[Andrew Jones]

On Tue, Nov 29, 2022 at 04:54:19PM +0000, Conor Dooley wrote:
> On Tue, Nov 29, 2022 at 05:12:23PM +0100, Andrew Jones wrote:
> > On Tue, Nov 29, 2022 at 02:47:42PM +0000, Conor Dooley wrote:
> > > While the list of rules may have been accurate when created, it now
> > > lacks some clarity in the face of isa-manual updates. Specifically:
> > > 
> > > - there is no mention here of a distinction between regular 'Z'
> > >   extensions which are "Additional Standard Extensions" and "Zxm"
> > >   extensions which are "Standard Machine-Level Extensions"
> > > 
> > > - there is also no explicit mention of where either should be sorted in
> > >   the list
> > > 
> > > - underscores are only required between two *multi-letter* extensions but
> > >   the list of rules implies that this is required between a multi-letter
> > >   extension and any other extension. IOW "rv64imafdzicsr_zifencei" is a
> > >   valid string
> > > 
> > > Attempt to clean up the list of rules, by adding information on the
> > > above & sprinkling in some white space for readability.
> > > 
> > > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > > ---
> > >  arch/riscv/kernel/cpu.c | 22 +++++++++++++++++-----
> > >  1 file changed, 17 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> > > index 852ecccd8920..5e42c92a8456 100644
> > > --- a/arch/riscv/kernel/cpu.c
> > > +++ b/arch/riscv/kernel/cpu.c
> > > @@ -120,20 +120,32 @@ device_initcall(riscv_cpuinfo_init);
> > >  		.uprop = #UPROP,				\
> > >  		.isa_ext_id = EXTID,				\
> > >  	}
> > > +
> > >  /*
> > >   * Here are the ordering rules of extension naming defined by RISC-V
> > >   * specification :
> > > - * 1. All extensions should be separated from other multi-letter extensions
> > > - *    by an underscore.
> > > + *
> > > + * 1. All multi-letter extensions should be separated from other multi-letter
> > > + *    extensions by an underscore.
> > > + *
> > >   * 2. The first letter following the 'Z' conventionally indicates the most
> > >   *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
> > > - *    If multiple 'Z' extensions are named, they should be ordered first
> > > - *    by category, then alphabetically within a category.
> > > + *    'Z' extensions should be sorted after single-letter extensions and before
> > > + *    any higher-privileged extensions.
> > > + *    If multiple 'Z' extensions are named, they should be ordered first by
> > > + *    category, then alphabetically within a category.
> > > + *
> > >   * 3. Standard supervisor-level extensions (starts with 'S') should be
> > >   *    listed after standard unprivileged extensions.  If multiple
> > >   *    supervisor-level extensions are listed, they should be ordered
> > >   *    alphabetically.
> > > - * 4. Non-standard extensions (starts with 'X') must be listed after all
> > > + *
> > > + * 4  Standard machine-level extensions (starts with 'Zxm') should be
> > > + *    listed after any lower-privileged, standard extensions.  If multiple
> > > + *    machine-level extensions are listed, they should be ordered
> > > + *    alphabetically.
> > > + *
> > > + * 5. Non-standard extensions (starts with 'X') must be listed after all
> > >   *    standard extensions. They must be separated from other multi-letter
> > >   *    extensions by an underscore.
> > >   */
> > > -- 
> > > 2.38.1
> > >
> > 
> > Alternatively, we could change the comment to just point out the spec
> > chapter and provide an example, e.g.
> 
> IDK, maybe add the reference & the example but keep the summary?

It risks needing to synchronize the comment with the spec. Also, the
comment doesn't need to reproduce the flexible specifications, since
Linux has a single implementation (it always puts an underscore between
single-letter extensions and the first multi-letter extension, for
example). So, rather than paraphrase too much of the spec, we could just
point out Linux's specific implementation (with the help of an example).

I don't feel that strongly about it though, so we can keep the text
the spec paraphrasing too.

Thanks,
drew

> 
> > /*
> >  * The canonical order of ISA extension names in the ISA string is defined in
> >  * chapter 27 of the unprivileged spec. An example string following the
> >  * order is
> >  *
> >  *   rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux
> >  *
> >  * Notice how Z-extensions are first sorted by category using the canonical
> >  * order of the first letter following the Z. Extension groups are in the
> >  * order specified in chapter 27. Extensions within each group are sorted
> >  * alphabetically.
> >  */
> > 
> > 
> > Thanks,
> > drew

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Re: [RFC 1/2] RISC-V: clarify ISA string ordering rules in cpu.c

[Conor Dooley]

On Tue, Nov 29, 2022 at 06:19:51PM +0100, Andrew Jones wrote:
> On Tue, Nov 29, 2022 at 04:54:19PM +0000, Conor Dooley wrote:
> > On Tue, Nov 29, 2022 at 05:12:23PM +0100, Andrew Jones wrote:
> > > On Tue, Nov 29, 2022 at 02:47:42PM +0000, Conor Dooley wrote:
> > > > While the list of rules may have been accurate when created, it now
> > > > lacks some clarity in the face of isa-manual updates. Specifically:
> > > > 
> > > > - there is no mention here of a distinction between regular 'Z'
> > > >   extensions which are "Additional Standard Extensions" and "Zxm"
> > > >   extensions which are "Standard Machine-Level Extensions"
> > > > 
> > > > - there is also no explicit mention of where either should be sorted in
> > > >   the list
> > > > 
> > > > - underscores are only required between two *multi-letter* extensions but
> > > >   the list of rules implies that this is required between a multi-letter
> > > >   extension and any other extension. IOW "rv64imafdzicsr_zifencei" is a
> > > >   valid string
> > > > 
> > > > Attempt to clean up the list of rules, by adding information on the
> > > > above & sprinkling in some white space for readability.
> > > > 
> > > > Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > > > ---
> > > >  arch/riscv/kernel/cpu.c | 22 +++++++++++++++++-----
> > > >  1 file changed, 17 insertions(+), 5 deletions(-)
> > > > 
> > > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> > > > index 852ecccd8920..5e42c92a8456 100644
> > > > --- a/arch/riscv/kernel/cpu.c
> > > > +++ b/arch/riscv/kernel/cpu.c
> > > > @@ -120,20 +120,32 @@ device_initcall(riscv_cpuinfo_init);
> > > >  		.uprop = #UPROP,				\
> > > >  		.isa_ext_id = EXTID,				\
> > > >  	}
> > > > +
> > > >  /*
> > > >   * Here are the ordering rules of extension naming defined by RISC-V
> > > >   * specification :
> > > > - * 1. All extensions should be separated from other multi-letter extensions
> > > > - *    by an underscore.
> > > > + *
> > > > + * 1. All multi-letter extensions should be separated from other multi-letter
> > > > + *    extensions by an underscore.
> > > > + *
> > > >   * 2. The first letter following the 'Z' conventionally indicates the most
> > > >   *    closely related alphabetical extension category, IMAFDQLCBKJTPVH.
> > > > - *    If multiple 'Z' extensions are named, they should be ordered first
> > > > - *    by category, then alphabetically within a category.
> > > > + *    'Z' extensions should be sorted after single-letter extensions and before
> > > > + *    any higher-privileged extensions.
> > > > + *    If multiple 'Z' extensions are named, they should be ordered first by
> > > > + *    category, then alphabetically within a category.
> > > > + *
> > > >   * 3. Standard supervisor-level extensions (starts with 'S') should be
> > > >   *    listed after standard unprivileged extensions.  If multiple
> > > >   *    supervisor-level extensions are listed, they should be ordered
> > > >   *    alphabetically.
> > > > - * 4. Non-standard extensions (starts with 'X') must be listed after all
> > > > + *
> > > > + * 4  Standard machine-level extensions (starts with 'Zxm') should be
> > > > + *    listed after any lower-privileged, standard extensions.  If multiple
> > > > + *    machine-level extensions are listed, they should be ordered
> > > > + *    alphabetically.
> > > > + *
> > > > + * 5. Non-standard extensions (starts with 'X') must be listed after all
> > > >   *    standard extensions. They must be separated from other multi-letter
> > > >   *    extensions by an underscore.
> > > >   */
> > > > -- 
> > > > 2.38.1
> > > >
> > > 
> > > Alternatively, we could change the comment to just point out the spec
> > > chapter and provide an example, e.g.
> > 
> > IDK, maybe add the reference & the example but keep the summary?
> 
> It risks needing to synchronize the comment with the spec.

Heh, see I almost see this as an *advantage* of this approach!

> Also, the
> comment doesn't need to reproduce the flexible specifications, since
> Linux has a single implementation (it always puts an underscore between
> single-letter extensions and the first multi-letter extension, for
> example). So, rather than paraphrase too much of the spec, we could just
> point out Linux's specific implementation (with the help of an example).

You're right here though. I've had my head stuck in the incoming-string
side of things rather than outgoing. I'll wait for the all clear from
Above, but ideally I'll reword this explaining where this info shows up
(and therefore why it needs to be ordered), what elements of the rules
matter here (entirely ordering) and then include your bits from below?

> I don't feel that strongly about it though, so we can keep the text
> the spec paraphrasing too.

> > > /*
> > >  * The canonical order of ISA extension names in the ISA string is defined in
> > >  * chapter 27 of the unprivileged spec. An example string following the
> > >  * order is
> > >  *
> > >  *   rv64imadc_zifoo_zigoo_zafoo_sbar_scar_zxmbaz_xqux_xrux
> > >  *
> > >  * Notice how Z-extensions are first sorted by category using the canonical
> > >  * order of the first letter following the Z. Extension groups are in the
> > >  * order specified in chapter 27. Extensions within each group are sorted
> > >  * alphabetically.
> > >  */


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[PATCH] Documentation: riscv: note that counter access is part of the uABI

[Conor Dooley]

Commit 5a5294fbe020 ("RISC-V: Re-enable counter access from userspace")
fixed userspace access to CYCLE, TIME & INSTRET counters and left a nice
comment in-place about why they must not be restricted. Since we now
have a uABI doc in RISC-V land, add a section documenting it.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
it to be applicable, just getting a patch into patchwork while I don't
forget about this.
---
 Documentation/riscv/uabi.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/riscv/uabi.rst b/Documentation/riscv/uabi.rst
index 8d2651e42fda..638ddce56700 100644
--- a/Documentation/riscv/uabi.rst
+++ b/Documentation/riscv/uabi.rst
@@ -3,6 +3,13 @@
 RISC-V Linux User ABI
 =====================
 
+Counter access
+--------------
+
+Access to the CYCLE, TIME and INSTRET counters, now controlled by the SBI PMU
+extension, were part of the ISA when the uABI was frozen & so remain accessible
+from userspace.
+
 ISA string ordering in /proc/cpuinfo
 ------------------------------------
 

base-commit: 13ee7ef407cfcf63f4f047460ac5bb6ba5a3447d
prerequisite-patch-id: d17a9ffb6fcf99eb683728da98cd50e18cd28fe8
prerequisite-patch-id: 0df4127e3f4a0c02a235fea00bcb69cd94fabb38
prerequisite-patch-id: 171724b870ba212b714ebbded480269accd83733
-- 
2.38.1


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Re: [PATCH] Documentation: riscv: note that counter access is part of the uABI

[Palmer Dabbelt]

On Thu, 01 Dec 2022 05:51:10 PST (-0800), Conor Dooley wrote:
> Commit 5a5294fbe020 ("RISC-V: Re-enable counter access from userspace")
> fixed userspace access to CYCLE, TIME & INSTRET counters and left a nice
> comment in-place about why they must not be restricted. Since we now
> have a uABI doc in RISC-V land, add a section documenting it.
>
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
> Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
> it to be applicable, just getting a patch into patchwork while I don't
> forget about this.
> ---
>  Documentation/riscv/uabi.rst | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/Documentation/riscv/uabi.rst b/Documentation/riscv/uabi.rst
> index 8d2651e42fda..638ddce56700 100644
> --- a/Documentation/riscv/uabi.rst
> +++ b/Documentation/riscv/uabi.rst
> @@ -3,6 +3,13 @@
>  RISC-V Linux User ABI
>  =====================
>
> +Counter access
> +--------------
> +
> +Access to the CYCLE, TIME and INSTRET counters, now controlled by the SBI PMU
> +extension, were part of the ISA when the uABI was frozen & so remain accessible
> +from userspace.
> +
>  ISA string ordering in /proc/cpuinfo
>  ------------------------------------
>
>
> base-commit: 13ee7ef407cfcf63f4f047460ac5bb6ba5a3447d
> prerequisite-patch-id: d17a9ffb6fcf99eb683728da98cd50e18cd28fe8
> prerequisite-patch-id: 0df4127e3f4a0c02a235fea00bcb69cd94fabb38
> prerequisite-patch-id: 171724b870ba212b714ebbded480269accd83733

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

I think I merged the last one of these, but if the doc folks pick it up 
that's fine with me.  Otherwise I'll take it when it comes back around, 
so folks have time to take a look.

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Re: [PATCH] Documentation: riscv: note that counter access is part of the uABI

[Jonathan Corbet]

Palmer Dabbelt <palmer@dabbelt.com> writes:

> On Thu, 01 Dec 2022 05:51:10 PST (-0800), Conor Dooley wrote:
>> Commit 5a5294fbe020 ("RISC-V: Re-enable counter access from userspace")
>> fixed userspace access to CYCLE, TIME & INSTRET counters and left a nice
>> comment in-place about why they must not be restricted. Since we now
>> have a uABI doc in RISC-V land, add a section documenting it.
>>
>> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>> ---
>> Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
>> it to be applicable, just getting a patch into patchwork while I don't
>> forget about this.
>> ---
>>  Documentation/riscv/uabi.rst | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/Documentation/riscv/uabi.rst b/Documentation/riscv/uabi.rst
>> index 8d2651e42fda..638ddce56700 100644
>> --- a/Documentation/riscv/uabi.rst
>> +++ b/Documentation/riscv/uabi.rst
>> @@ -3,6 +3,13 @@
>>  RISC-V Linux User ABI
>>  =====================
>>
>> +Counter access
>> +--------------
>> +
>> +Access to the CYCLE, TIME and INSTRET counters, now controlled by the SBI PMU
>> +extension, were part of the ISA when the uABI was frozen & so remain accessible
>> +from userspace.
>> +
>>  ISA string ordering in /proc/cpuinfo
>>  ------------------------------------
>>
>>
>> base-commit: 13ee7ef407cfcf63f4f047460ac5bb6ba5a3447d
>> prerequisite-patch-id: d17a9ffb6fcf99eb683728da98cd50e18cd28fe8
>> prerequisite-patch-id: 0df4127e3f4a0c02a235fea00bcb69cd94fabb38
>> prerequisite-patch-id: 171724b870ba212b714ebbded480269accd83733
>
> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
>
> I think I merged the last one of these, but if the doc folks pick it up 
> that's fine with me.  Otherwise I'll take it when it comes back around, 
> so folks have time to take a look.

"Doc folks" applied it, thanks. :)

jon

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Re: [PATCH] Documentation: riscv: note that counter access is part of the uABI

[Jonathan Corbet]

Jonathan Corbet <corbet@lwn.net> writes:

> Palmer Dabbelt <palmer@dabbelt.com> writes:
>> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
>> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
>>
>> I think I merged the last one of these, but if the doc folks pick it up 
>> that's fine with me.  Otherwise I'll take it when it comes back around, 
>> so folks have time to take a look.
>
> "Doc folks" applied it, thanks. :)

Actually, I take that back.  I'd missed this part from the patch:

> Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
> it to be applicable, just getting a patch into patchwork while I don't
> forget about this.

...but b4 happily picked up a couple of *other* patches from this thread
and applied them instead; I've now undone that.  Sorry for the noise.

jon

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Re: [PATCH] Documentation: riscv: note that counter access is part of the uABI

[Conor Dooley]

[-- Attachment #1.1: Type: text/plain, Size: 1238 bytes --]

On Sat, Dec 03, 2022 at 03:45:35AM -0700, Jonathan Corbet wrote:
> Jonathan Corbet <corbet@lwn.net> writes:
> 
> > Palmer Dabbelt <palmer@dabbelt.com> writes:
> >> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
> >> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> >>
> >> I think I merged the last one of these, but if the doc folks pick it up 
> >> that's fine with me.  Otherwise I'll take it when it comes back around, 
> >> so folks have time to take a look.
> >
> > "Doc folks" applied it, thanks. :)
> 
> Actually, I take that back.  I'd missed this part from the patch:
> 
> > Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
> > it to be applicable, just getting a patch into patchwork while I don't
> > forget about this.
> 
> ...but b4 happily picked up a couple of *other* patches from this thread
> and applied them instead; I've now undone that.  Sorry for the noise.

Huh, I accidentally put an "in-reply-to" header on this patch. I have
been updating some of my submission helper scripts & I must have left
the field populated from sending another set by accident:
https://lore.kernel.org/linux-riscv/20221129144742.2935581-1-conor.dooley@microchip.com/

Apologies!


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Re: [PATCH] Documentation: riscv: note that counter access is part of the uABI

[Atish Patra]

On Sat, Dec 3, 2022 at 2:57 AM Conor Dooley <conor@kernel.org> wrote:
>
> On Sat, Dec 03, 2022 at 03:45:35AM -0700, Jonathan Corbet wrote:
> > Jonathan Corbet <corbet@lwn.net> writes:
> >
> > > Palmer Dabbelt <palmer@dabbelt.com> writes:
> > >> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
> > >> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> > >>
> > >> I think I merged the last one of these, but if the doc folks pick it up
> > >> that's fine with me.  Otherwise I'll take it when it comes back around,
> > >> so folks have time to take a look.
> > >
> > > "Doc folks" applied it, thanks. :)
> >
> > Actually, I take that back.  I'd missed this part from the patch:
> >
> > > Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
> > > it to be applicable, just getting a patch into patchwork while I don't
> > > forget about this.
> >
> > ...but b4 happily picked up a couple of *other* patches from this thread
> > and applied them instead; I've now undone that.  Sorry for the noise.
>
> Huh, I accidentally put an "in-reply-to" header on this patch. I have
> been updating some of my submission helper scripts & I must have left
> the field populated from sending another set by accident:
> https://lore.kernel.org/linux-riscv/20221129144742.2935581-1-conor.dooley@microchip.com/
>

I don't see the patch upstream. Is this patch merged already ?
If not, please hold on merging this for now. We had some discussions
around this in the perf community.
Here is the thread
https://lore.kernel.org/lkml/Y7gN32eHJNyWBvVD@FVFF77S0Q05N/T/

TLDR; Even though x86 allows unrestricted access through rdpmc (not
default), it still reads zero unless a privileged root user modifies
the MSR interface exposed by the kernel.

Quoting PeterZ

"RDPMC is only useful if you read counters you own on yourself -- IOW
selfmonitoring, using the interface outlined in uapi/linux/perf_events.h
near struct perf_event_mmap_page.

Any other usage -- you get to keep the pieces."

"Anyway, given RISC-V being a very young platform, I would try really
*really* *REALLY* hard to stomp on these applications and get them to
change in order to reclaim the PMU usage."

We need to decide what's the best approach for RISC-V. The current
text in uABI will let users assume that
cycle/instret can be read without any issues which is wrong.

There are few options what we can do for RISC-V:

1. We can trap n emulate and report 0 always as suggested by Mark in
that thread.
2. Continue to allow the user to read the counters directly but
expects the garbage value depending on the other activities
on the system. Hopefully, folks will fix their application by that time.

Once we have the procfs interface, we enforce the behavior by breaking
the application.

In either case, the uABI needs to be updated accordingly.

> Apologies!
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv



--
Regards,
Atish

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Re: [PATCH] Documentation: riscv: note that counter access is part of the uABI

[Conor Dooley]

[-- Attachment #1.1: Type: text/plain, Size: 3572 bytes --]

On Mon, Jan 09, 2023 at 01:36:19PM -0800, Atish Patra wrote:
> On Sat, Dec 3, 2022 at 2:57 AM Conor Dooley <conor@kernel.org> wrote:
> >
> > On Sat, Dec 03, 2022 at 03:45:35AM -0700, Jonathan Corbet wrote:
> > > Jonathan Corbet <corbet@lwn.net> writes:
> > >
> > > > Palmer Dabbelt <palmer@dabbelt.com> writes:
> > > >> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
> > > >> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> > > >>
> > > >> I think I merged the last one of these, but if the doc folks pick it up
> > > >> that's fine with me.  Otherwise I'll take it when it comes back around,
> > > >> so folks have time to take a look.
> > > >
> > > > "Doc folks" applied it, thanks. :)
> > >
> > > Actually, I take that back.  I'd missed this part from the patch:
> > >
> > > > Based on an, as yet, unsent v2 of my other uABI changes. I don't expect
> > > > it to be applicable, just getting a patch into patchwork while I don't
> > > > forget about this.
> > >
> > > ...but b4 happily picked up a couple of *other* patches from this thread
> > > and applied them instead; I've now undone that.  Sorry for the noise.
> >
> > Huh, I accidentally put an "in-reply-to" header on this patch. I have
> > been updating some of my submission helper scripts & I must have left
> > the field populated from sending another set by accident:
> > https://lore.kernel.org/linux-riscv/20221129144742.2935581-1-conor.dooley@microchip.com/
> >
> 
> I don't see the patch upstream. Is this patch merged already ?

No it's not. I was going to resend it actually, but I noticed the thread
yesterday or something. Not sure why you CC'ed half the world on it but
not linux-riscv? Or me if you didn't want me resending it!

> If not, please hold on merging this for now. We had some discussions
> around this in the perf community.
> Here is the thread
> https://lore.kernel.org/lkml/Y7gN32eHJNyWBvVD@FVFF77S0Q05N/T/
> 
> TLDR; Even though x86 allows unrestricted access through rdpmc (not
> default), it still reads zero unless a privileged root user modifies
> the MSR interface exposed by the kernel.
> 
> Quoting PeterZ
> 
> "RDPMC is only useful if you read counters you own on yourself -- IOW
> selfmonitoring, using the interface outlined in uapi/linux/perf_events.h
> near struct perf_event_mmap_page.
> 
> Any other usage -- you get to keep the pieces."
> 
> "Anyway, given RISC-V being a very young platform, I would try really
> *really* *REALLY* hard to stomp on these applications and get them to
> change in order to reclaim the PMU usage."
> 
> We need to decide what's the best approach for RISC-V. The current
> text in uABI will let users assume that
> cycle/instret can be read without any issues which is wrong.
> 
> There are few options what we can do for RISC-V:
> 
> 1. We can trap n emulate and report 0 always as suggested by Mark in
> that thread.
> 2. Continue to allow the user to read the counters directly but
> expects the garbage value depending on the other activities
> on the system. Hopefully, folks will fix their application by that time.
> 
> Once we have the procfs interface, we enforce the behavior by breaking
> the application.
> 
> In either case, the uABI needs to be updated accordingly.

I don't disagree with what I saw either PeterZ or Mark say. I'm happy
not to resend this, I've got no skin in the game other than not wanting
something like that "documented" only in the driver.

What do you intend doing to instigate the "stomping"?

Thanks,
Conor.


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