linux-kernel - Re: [PATCH v2] vdso: Remove struct getcpu

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Message-ID: <e95dc212-6fd3-43e3-aeb7-bf55917e0cd4@intel.com>
Date: Mon, 13 Oct 2025 07:06:55 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
 Huacai Chen <chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>,
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
 Alexander Gordeev <agordeev@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>, Andy Lutomirski <luto@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
 Richard Weinberger <richard@....at>,
 Anton Ivanov <anton.ivanov@...bridgegreys.com>,
 Johannes Berg <johannes@...solutions.net>,
 Vincenzo Frascino <vincenzo.frascino@....com>, Shuah Khan <shuah@...nel.org>
Cc: loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-s390@...r.kernel.org, linux-um@...ts.infradead.org,
 linux-api@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2] vdso: Remove struct getcpu_cache

On 10/13/25 02:20, Thomas Weißschuh wrote:
> -int __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused);
> -int __vdso_getcpu(unsigned int *cpu, unsigned int *node, struct getcpu_cache *unused)
> +int __vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused);
> +int __vdso_getcpu(unsigned int *cpu, unsigned int *node, void *unused)
>  {
>  	int cpu_id;

It would ideally be nice to have a _bit_ more history on this about
how it became unused any why there is such high confidence that
userspace never tries to use it.

Let's say someone comes along in a few years and wants to use this
'unused' parameter. Could they?