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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mon, 13 Feb 2017 13:44:42 -0800
Message-ID: <CA+55aFyYBLHFpGYiwdDT_i6mkFcS-c=o4aVJy49UkHitDEGZsw@mail.gmail.com>
Subject: Re: Linux 4.9.6 ( Restore IO-APIC irq_chip retrigger callback ,
 breaks my box )
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Gabriel C <nix.or.die@gmail.com>,
        Mike Galbraith <efault@gmx.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable <stable@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ruslan Ruslichenko <rruslich@cisco.com>,
        Jiri Slaby <jslaby@suse.cz>
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On Mon, Feb 13, 2017 at 1:35 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>
>
> arch/x86/platform/goldfish/goldfish.c
>
> static int __init goldfish_init(void)
> {
>         platform_device_register_simple("goldfish_pdev_bus", -1,
>                                                 goldfish_pdev_bus_resources, 2);
>         return 0;
> }
> device_initcall(goldfish_init);
>
> So it unconditionallyt registers that platform device, which has IRQ 4 as
> irq resource and the driver happily matches on the platform devices.
>
> Wonderful crap, isn't it? It should be made 'depend on BROKEN'.

Ugh. Yeah, that's crazy. Random hardcoded interfaces that get enabled
by people by mistake.

And yeah, it's not just the irq. It just randomly sets up memory addresses too.

That thing needs to be disabled some way. Maybe not marked "broken",
but there needs to be something that actually enables it at runtime
(like a kernel command line option or something like that).

That said - that code was presumably enabled before too, so why would
this break something? And if this is the cause, we need to figure out
what it is that it then triggers..

            Linus