linux-kernel - Re: [PATCH 3/9] x86: vdso: Introduce asm/vdso/page.h

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Message-Id: <11527a80-7453-4624-b406-e88c5692b015@app.fastmail.com>
Date: Fri, 06 Sep 2024 19:19:46 +0000
From: "Arnd Bergmann" <arnd@...db.de>
To: "Vincenzo Frascino" <vincenzo.frascino@....com>,
 linux-kernel@...r.kernel.org, Linux-Arch <linux-arch@...r.kernel.org>,
 linux-mm@...ck.org
Cc: "Andy Lutomirski" <luto@...nel.org>,
 "Thomas Gleixner" <tglx@...utronix.de>,
 "Jason A . Donenfeld" <Jason@...c4.com>,
 "Christophe Leroy" <christophe.leroy@...roup.eu>,
 "Michael Ellerman" <mpe@...erman.id.au>,
 "Nicholas Piggin" <npiggin@...il.com>, "Naveen N Rao" <naveen@...nel.org>,
 "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
 "Dave Hansen" <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, "Theodore Ts'o" <tytso@....edu>,
 "Andrew Morton" <akpm@...ux-foundation.org>,
 "Steven Rostedt" <rostedt@...dmis.org>,
 "Masami Hiramatsu" <mhiramat@...nel.org>,
 "Mathieu Desnoyers" <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 3/9] x86: vdso: Introduce asm/vdso/page.h

On Fri, Sep 6, 2024, at 11:20, Vincenzo Frascino wrote:
> On 04/09/2024 15:52, Arnd Bergmann wrote:
>> On Tue, Sep 3, 2024, at 15:14, Vincenzo Frascino wrote:
> Looking at the definition of PAGE_SIZE and PAGE_MASK for each architecture they
> all depend on CONFIG_PAGE_SHIFT but they are slightly different, e.g.:
>
> x86:
> #define PAGE_SIZE        (_AC(1,UL) << PAGE_SHIFT)
>
> powerpc:
> #define PAGE_SIZE        (ASM_CONST(1) << PAGE_SHIFT)
>
> hence I left to the architecture the responsibility of redefining the constants
> for the VSDO.

ASM_CONST() is a powerpc-specific macro that is defined the
same way as _AC(). We could probably just replace all ASM_CONST()
as a cleanup, but for this purpose, just remove the custom PAGE_SIZE
and PAGE_SHIFT macros. This can be a single patch fro all
architectures.

    Arnd