x86: Spurious vectors not handled robustly

[Jan Kiszka]

Hi all,

probably since "x86: Avoid building unused IRQ entry stubs" (2414e021ac8d), the 
kernel can no longer tell spurious IRQs by the APIC apart from spuriously 
triggered unused vectors. We've managed to trigger such a cause with the 
Jailhouse hypervisor (incorrectly injected MANAGED_IRQ_SHUTDOWN_VECTOR), and the 
result was not only a misreport of the vector number (0xff instead of 0xef - 
took me a while...), but also stalled interrupts of equal and lower priority 
because a spurious interrupt is not (and must not be) acknowledged.

How to address that best? I would say we should at least have separate entry 
paths for APIC interrupt vs. vectors, to improve robustness in the faulty case.

Jan

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Siemens AG, Corporate Technology, CT RDA IOT SES-DE
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