linux-kernel - Re: [RESENT PATCH] arm64: cpuinfo: Add "model name" in /proc/cpuinfo for 64bit tasks also

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Date:   Tue, 2 Feb 2021 13:09:02 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Tianling Shen <cnsztl@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-kernel@...r.kernel.org, Sumit Gupta <sumitg@...dia.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will@...nel.org>,
        Dave Martin <Dave.Martin@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RESENT PATCH] arm64: cpuinfo: Add "model name" in /proc/cpuinfo
 for 64bit tasks also

On 2021-02-01 23:58, Tianling Shen wrote:
> From: Sumit Gupta <sumitg@...dia.com>
> 
> Removed restriction of displaying model name for 32 bit tasks only.
> This can be used for 64 bit tasks as well, and it's useful for some
> tools that already parse this, such as coreutils `uname -p`, Ubuntu
> model name display etc.

How exactly is it useful? It clearly isn't necessary for compatibility, 
since AArch64 userspace has apparently been running quite happily for 8 
years without it. It also doesn't convey anything meaningful to the 
user, since they already know they're on an Armv8-compatible processor 
by the fact that they're running AArch64 userspace at all.

Robin.

> It should be like this:
> ```
> $ cat '/proc/cpuinfo' | grep 'model name' | head -n 1
> model name : ARMv8 Processor rev X (v8l)
> ```
> 
> Link: https://lore.kernel.org/lkml/1472461345-28219-1-git-send-email-sumitg@nvidia.com/
> 
> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> Signed-off-by: Tianling Shen <cnsztl@...il.com>
> ---
>   arch/arm64/kernel/cpuinfo.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 77605aec25fe..d69b4e486098 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -148,8 +148,7 @@ static int c_show(struct seq_file *m, void *v)
>   		 * "processor".  Give glibc what it expects.
>   		 */
>   		seq_printf(m, "processor\t: %d\n", i);
> -		if (compat)
> -			seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",
> +		seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",
>   				   MIDR_REVISION(midr), COMPAT_ELF_PLATFORM);
>   
>   		seq_printf(m, "BogoMIPS\t: %lu.%02lu\n",
>