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I have a server with 6 dual port FibreChannel HBA's in it (12 PCIe functions / device instances).
Each device instance can have up to 32 MSI-X interrupt vectors as defined in the HBA's PCI config space.
When I load the OEM driver for the devices, device manager shows each was assigned 32 IRQs under the resources tab, for a total of 12*32 = 384 MSI-X interrupts among all the instances.
When I load my KMDF driver, 8 of the instances are given 32 vectors, and the remaining 4 are given only 1. This is with no MessageNumberLimit set in the registry.
If I disable 3 of the remaining instances and play around with the MessageNumberLimit on the 9th instance, I find I can get the total number of MSI-X interrupts up to about 273 or so.
The first 8 are assigned 32 and the 9th can have it's MessageNumberLimit set to 17 and it will be assigned 17 IRQs. If I bump it up to 18 (total of 274), I seem to go over some threshold and it only get's assigned 1 MSI-X vector.
If I set the MessageNumberLimit to 16 for each device instance, then all 12 instances are assigned 16 MSI-X vectors.
With all of that said, my question is:
Why can the OEM driver have 32 MSI-X vectors assigned to each of the 12 instances but my KMDF driver apparently cannot?
I assume the OEM driver is an older WDM based driver, but I don't know that for sure.
Is there some sort of limit built in to the KMDF/WDF framework?
Server is a SuperMicro with two 8 core Intel Xeon Silver 4215R CPUs.
32 GB of RAM
Windows Server 2019.
FibreChannel HBAs are PCIe 3.0
KMDF is 1.19
Thanks for any light you can shed on this discrepancy,
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