[Xen-devel] [RFC] Spurious PIC interrupts

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Since Jan's patch to print and mask bogus PIC vectors, we have found
some issues on older hardware were supurious PIC vectors are being
repeatedly logged, as spurious vectors will ignore the relevant mask bit.

The log message is deceptive in the case of a spurious vector.  I have
attached an RFC patch which changes the bogus_8259A_irq logic to be able
to detect spurious vectors and be rather less verbose about them.

The new bogus_8259A_irq() function is basically a copy of
_mask_and_ack_8259A_irq(), but returning a boolean indicating whether it
was a genuine interrupt or not, which controls whether the "No irq
handler" message in do_IRQ gets printed or not.

Jan: are you happy with the style of the adjustment, or could you
suggest a better way of doing it?

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com

Attachment: pic-bogus-spurious.patch
Description: Text Data

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