On 24/11/2022 17:34, Samuel Ortiz wrote:

On Thu, Nov 24, 2022 at 05:20:37PM +0000, Conor Dooley wrote:

quoted

On 24/11/2022 17:12, Samuel Ortiz wrote:

quoted

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On Thu, Nov 24, 2022 at 11:55:01AM +0000, Conor Dooley wrote:

quoted

On Thu, Nov 24, 2022 at 11:47:30AM +0100, Samuel Ortiz wrote:

quoted

Patch #1 is definitely needed regardless of which interface we pick for
exposing the ISA strings to userspace.

I took another look at #1, and I feel more confused about what
constitutes canonical order than I did before! If you know better than
I, and you probably do since you're interested in these 6 month old
patches, some insight would be appreciated!

Assuming we don't go with hwcap, I dont think the order of the
riscv_isa_ext_id enum matters that much?

The chief put it in canonical order so that's good enough for me!

quoted

iiuc we're building the cpuinfo string from the riscv_isa_ext_data
array, and I think the current code is incorrect:

static struct riscv_isa_ext_data isa_ext_arr[] = {
    __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),
};

zicbom and zihintpause should come before supervisor level extensions.
I'm going to send a patch for that.

idk, Palmer explicitly re-ordered this:
https://lore.kernel.org/linux-riscv/20220920204518.10988-1-palmer@rivosinc.com/ (local)

By my reading of the isa manual, what Palmer did is correct as
those are not "Additional Standard Extensions". /shrug

Hmm, by their name (Z[a-b]+) they are Additional Standard Extensions.
What am I missing?

Right, and this is where I get confused. Zam and Ztso *are* Additional
Standard Extensions, I think we can agree on that one? For those
extensions:
\chapter{``Ztso'' Standard Extension for Total Store Ordering, v0.1}
\chapter{``Zam'' Standard Extension for Misaligned Atomics, v0.1}

They're also called out specifically in the table:
https://github.com/riscv/riscv-isa-manual/blob/master/src/naming.tex#L147

For Zihintpause however:
\chapter{``Zihintpause'' Pause Hint, Version 2.0}

See what I mean? I looked at the specs for the bitmanip stuff and for
crypto, which both never mention being standard.

That table has the caption:

The table also 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. 

It only calls out Zicsr, Zifencei, Zam and Ztso are being permitted
before Sdef, but as I said I am not a specs person, so perhaps some
of the extensions in question are intended to go there but have not
yet been merged into the isa manual doc. Zihintpause *is* in the
isa manual though but not specifically called out.

Anyways, hopefully that at least helps with my line of thinking!

Conor.