Comment 9 for bug 1508593

After working on the backport to Vivid, I'm not sure if the patch(Commit c0ff971) requested in this bug is applicable to Vivid and Trusty.

Commit c0ff971 disables interrupts when re-routing legacy IRQs. However, the functions affected by commit c0ff971 were not added until v4.2-rc1 by commit:
'49c7e60 x86/irq: Implement callbacks to enable hierarchical irqdomains on IOAPICs'

Heirarchical irqdomains were not added until v4.2-rc1 as well, by commit:
'b5dc8e6 x86/irq: Use hierarchical irqdomain to manage CPU interrupt vectors'

The reproducer listed in the description cannot be attempted since mp_setup_entry() and mp_register_handler() dont exist in the 3.19 or 3.13 kernels since they were added in 4.2-rc1 by commit 49c7e60.

Is there a way to confirm and test that commit c0ff971 is needed in Vivid and Trusty?