linux-kernel - Re: [PATCH] x86/i8259: Work around buggy legacy PIC

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Message-ID: <c26954e1-bb2f-086a-9c7f-68382978efe7@zytor.com>
Date:   Fri, 14 May 2021 10:35:57 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Sachi King <nakato@...ato.io>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        David Laight <David.Laight@...lab.com>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/i8259: Work around buggy legacy PIC

On 5/14/21 10:32 AM, Thomas Gleixner wrote:
> 
> That's a valid assumption. As I said, we can make IOAPIC work even w/o
> PIC. I'll have a look how much PIC assumptions are still around.
> 

As far as I read, the problem isn't actually the absence of a PIC (we 
definitely boot systems without PICs all the time now), but rather that 
the PIC is advertised in ACPI but is buggy or absent; a similar platform 
with different firmware doesn't have problem.

If my understanding of the thread is correct, it's quirk fodder.

	-hpa