The effective_affinity_mask is always set when an interrupt is assigned in
__assign_irq_vector() -> apic->cpu_mask_to_apicid(), e.g. for struct apic
apic_physflat: -> default_cpu_mask_to_apicid() ->
irq_data_update_effective_affinity(), but it looks d->common->affinity
remains all-1's before the user space or the kernel changes it later.

In the early allocation/initialization phase of an IRQ, we should use the
effective_affinity_mask, otherwise Hyper-V may not deliver the interrupt to
the expected CPU.  Without the patch, if we assign 7 Mellanox ConnectX-3
VFs to a 32-vCPU VM, one of the VFs may fail to receive interrupts.
Tested-by: NAdrian Suhov <v-adsuho@microsoft.com>
Signed-off-by: NDexuan Cui <decui@microsoft.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NJake Oshins <jakeo@microsoft.com>
Cc: stable@vger.kernel.org
Cc: Jork Loeser <jloeser@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>