linux-kernel - Re: [PATCH RFC] arm64: improve display about CPU architecture in cpuinfo

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Date:   Mon, 7 Mar 2022 20:30:07 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Rongwei Wang <rongwei.wang@...ux.alibaba.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, joey.gouly@....com,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] arm64: improve display about CPU architecture in cpuinfo

On Mon, Mar 7, 2022 at 5:48 PM Robin Murphy <robin.murphy@....com> wrote:

> And arguably it's not even too late, because 10 years ago this *did* say
> "AArch64". I don't remember all the exact details behind commit
> 44b82b7700d0 ("arm64: Fix up /proc/cpuinfo") - this just tickled enough
> of a memory to go and look up the git history - but I don't think we
> changed any of those fields without a real reason.
>

The patch description does state that this was done for compatibility with
32-bit architectures, which does make some sense. I suppose for similar
reasons, the arch/arm/ version of /proc/cpuinfo is now stuck at
'CPU architecture: 7', even for ARMv8 or higher in aarch32 mode.

The part that I find more annoying is how we leave out the one bit
of information that people are generally looking for in /proc/cpuinfo:
the name of the processor. Even though we already know the
exact processor type in order to handle the CPU errata, this is
always "model name\t: ARMv7 Processor rev %d (v7l)" on 32-bit,
and "model name\t: ARMv8 Processor rev %d (%s)" on 64-bit,
with the revision being the least important bit of information here...

        Arnd