linux-kernel - Re: [PATCH v3 2/3] RISC-V: uapi: add HWCAP for Bitmanip/Scalar Crypto

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Message-ID: <Y3+mBAV8oxphjHcJ@vermeer>
Date:   Thu, 24 Nov 2022 18:12:36 +0100
From:   Samuel Ortiz <sameo@...osinc.com>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     "Hongren (Zenithal) Zheng" <i@...ithal.me>,
        Palmer Dabbelt <palmer@...osinc.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <atishp@...osinc.com>,
        Anup Patel <anup@...infault.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>, linux-mm@...ck.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org,
        Michael Kerrisk <mtk.manpages@...il.com>,
        linux-man@...r.kernel.org, Jiatai He <jiatai2021@...as.ac.cn>,
        Heiko Stuebner <heiko@...ech.de>
Subject: Re: [PATCH v3 2/3] RISC-V: uapi: add HWCAP for Bitmanip/Scalar Crypto

On Thu, Nov 24, 2022 at 11:55:01AM +0000, Conor Dooley wrote:
> On Thu, Nov 24, 2022 at 11:47:30AM +0100, Samuel Ortiz wrote:
> 
> > 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?

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.

And the Zb/Zk ones should come after the Zi ones, and before the
supervisor level ones (The I category comes before the B or the K one).
So we should check that when patch #1 is rebased.

Cheers,
Samuel.