GPUDirect IO Window Size

Is there a way to increase the IO window size available for GPUDirect? I’m working with a 3rd party driver that wants about 640MB of pinned memory. However, I can’t seem to pin more than 210MB at once. According to lspci, the largest memory hole for the GPU is 256MB, which is why I believe pin requests beyond ~210MB begin to fail.

Is there a way to increase this? AFAIK this is something that must be advertised by the PCIe endpoint when it comes up. Is there a utility available that can modify a non-volatile register, or something?