linux-kernel - Re: [PATCH RESEND v2] x86: warn on native_io

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Message-ID: <YcRYD9drK5lRgEyY@zn.tnic>
Date:   Thu, 23 Dec 2021 12:05:51 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Mateusz Jończyk <mat.jonczyk@...pl>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH RESEND v2] x86: warn on native_io_delay() before DMI scan

On Sun, Oct 17, 2021 at 09:25:58PM +0200, Mateusz Jończyk wrote:
> Writing to IO port 0x80 in native_io_delay() causes system lockups on
> some laptops. This is handled by io_delay_init(), which scans DMI info
> and changes io_delay_type on these laptops.
> 
> Therefore, calling native_io_delay() / outb_p() / inb_p() / etc. before
> io_delay_init() may cause problems there and may constitute a kernel
> bug. Warn if this happens.

When/how does this happen?

io_delay_init() gets called pretty early in setup_arch()...

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette