On Tue, Sep 27, 2016@11:39:53AM -0700, Nisha Miller wrote:

Hi,

We plugged our NVMe controller into a server running Kernel 3.19.8 and
we were able to create multiple IO queues.

On the same server, if we boot Kernel 2.6.32 we can create only 1 IO
queue. On 2.6.32, pci_enable_msi_block() always returns number of MSIs
supported as 1. Since there is no change in the hardware, I'm
wondering where the problem lies and how we can fix this.

Any clues, ideas, tips greatly appreciated!

In a 2.6.32 kernel on x86, then enabling code should be going through
arch_setup_msi_irqs, which says it doesn't support multiple MSI's "yet".
You can only do 1 MSI on such an old kernel.