[Xen-devel] another regression from IRQ handling changes

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

An issue I had fixed a little while before your changes now appears to
exist again (can't actively verify it due to lack of access to a sufficiently
big system): While we now can handle more than 192 interrupt sources,
those again are confined to the first 256 IO-APIC pins. We know,
however, that there are systems with well over 300 pins (most of which
are typically unused, and hence being able to "only" handle 192 interrupt
sources doesn't really present a problem on these systems.

Clearly, handling of more than 256 (non-MSI) interrupt sources cannot
be done without a kernel side change, since there needs to be a
replacement for the 8-bit vector information conveyed through the
kernel writes to the IO-APIC redirection table entries. However, up to
256 interrupt sources could easily be handled without kernel side
change, by making PHYSDEVOP_alloc_irq_vector return a fake vector
(rather than the unmodified irq that got passed in).

Thoughts?

Thanks, Jan


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