issues with MSI interrupts

Cannot seem to obtain more than a single MSI interrupt.
pci_all_irq_vectors (dev n, m, PCI_IRQ_MSI) fails -ENOSPC for anything except n=1.
pci_msi_vec_count(dev) returns 8, which matches the lspci -vv output for the device.
Our kernel (5.14.0-70.13.1.el9_0.x86_64) already has CONFIG_IRQ_REMAP=1, and CONFIG_INTEL_IOMMU=1, which seems to be the most suggested solutions.

I also notice that with this version of the kernel, functions like pci_enable_msi_range() are no longer available.