linux-kernel - Re: [PATCH 3/3] x86/asm: Add support for WBNOINVD instruction

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Message-ID: <alpine.DEB.2.21.1803151017120.1525@nanos.tec.linutronix.de>
Date:   Thu, 15 Mar 2018 10:21:40 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
cc:     Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH 3/3] x86/asm: Add support for WBNOINVD instruction

On Fri, 19 Jan 2018, Kirill A. Shutemov wrote:

> This patch implements infrastructure to call WBNOINVD instruction.

grep 'This patch' Documentation/process/

> The basic idea is to match what we have for WBINVD.

Is it just an idea or is it actually doing it?

> The instruction is defined as WBINVD with REP (0xf3) prefix. If the
> machine doesn't support the instruction the prefix will be ignored and
> we would fallback to WBINVD.

We fallback? We do nothing.

The CPU ignores the prefix and falls back to WBINVD, right?

> +
> +#define wbnoinvd_on_cpu(cpu)     wbnoinvd()
> +static inline int wbnoinvd_on_all_cpus(void)

Bah. Please stop glueing defines in front of the function body. That's just
makes it harder to read.

Thanks,

	tglx