unable to set smp_affinity of PCIe interrupt

Hello,       Following is the output of cat /proc/interrupts                       CPU0       CPU1       CPU2 200:       9634          0          0  PCIe0-MSI  eth0 I want to change the processor affinity of the above PCIe interrupt By executing command echo 2 > /proc/irq/200/smp_affinity I get the following error sh: write error: Input/output error Even after changing the file permissions I have the same problem. I would like to know how to change the affinity of the above virtual interrupt?? Regards, Amit.