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SubjectRe: [PATCH 0/2] Add boot interrupt quirk mechanism for Xeon chipsets
Sean V Kelley <> 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 <>

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