linux-kernel - Re: [PATCH v2] x86/PCI: Improve log message when IRQ cannot be identified

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Message-ID: <alpine.DEB.2.21.2202031858490.34636@angie.orcam.me.uk>
Date:   Thu, 3 Feb 2022 19:09:19 +0000 (GMT)
From:   "Maciej W. Rozycki" <macro@...am.me.uk>
To:     Brent Spillner <spillner@....org>
cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, tglx@...utronix.de,
        Ingo Molnar <mingo@...hat.com>, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86/PCI: Improve log message when IRQ cannot be
 identified

On Thu, 3 Feb 2022, Brent Spillner wrote:

> > If your system has ACPI, I think "pci=biosirq" and "acpi=noirq" are at
> > best distractions from finding the real problem.
> 
> ...except when the cause is indeed buggy ACPI firmware, which is
> presumably the only reason these options exist in the first place.

 The former is really for us missing a PIRQ router or for a BIOS missing a 
$PIR table.  I have been posting patches recently to add support for some 
of such systems identified.  Those are all pre-ACPI, possibly long before, 
i.e. early to late 1990s (486 and P5/P54C Pentium and similar systems), 
and I think the option was added before we had ACPI support too.  I have a 
couple of pre-ACPI x86 systems too, which are quirky to say the least even 
though they were the quality systems of the time from reputable vendors.

 FWIW,

  Maciej