linux-kernel - Re: [PATCH 0/2] Add boot interrupt quirk mechanism for Xeon chipsets

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Message-ID: <8736bctd7a.fsf@nanos.tec.linutronix.de>
Date:   Sat, 15 Feb 2020 10:24:57 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Sean V Kelley <sean.v.kelley@...ux.intel.com>, bhelgaas@...gle.com,
        corbet@....net, mingo@...hat.com, bp@...en8.de
Cc:     x86@...nel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kar.hin.ong@...com, sassmann@...nic.de,
        Sean V Kelley <sean.v.kelley@...ux.intel.com>
Subject: Re: [PATCH 0/2] Add boot interrupt quirk mechanism for Xeon chipsets

Sean V Kelley <sean.v.kelley@...ux.intel.com> writes:
> When IRQ lines on secondary or higher IO-APICs are masked (e.g.,
> Real-Time threaded interrupts), many chipsets redirect IRQs on
> this line to the legacy PCH and in turn the base IO-APIC in the
> system. The unhandled interrupts on the base IO-APIC will be
> identified by the Linux kernel as Spurious Interrupts and can
> lead to disabled IRQ lines.
>
> Disabling this legacy PCI interrupt routing is chipset-specific and
> varies in mechanism between chipset vendors and across generations.
> In some cases the mechanism is exposed to BIOS but not all BIOS
> vendors choose to pick it up. With the increasing usage of RT as it
> marches towards mainline, additional issues have been raised with
> more recent Xeon chipsets.
>
> This patchset disables the boot interrupt on these Xeon chipsets where
> this is possible with an additional mechanism.  In addition, this
> patchset includes documentation covering the background of this quirk.

Well done! The documentation is really appreciated!

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>