Jared McNeill <jmcne...@invisible.ca> wrote: >On Wed, 28 Nov 2018, Jaromír Doleček wrote: > >> pci_intr_alloc() checks what the device claims to support down the >> call stack, reading the PCI config space. I assume there some >> negotiation between the PCI bus and the device. I hope device can't >> claim to support e.g. MSI-X if the bus doesn't. > >Device claiming to support MSI-X is fine. The bus should only set >PCI_FLAGS_MSIX_OKAY in its pcibus_attach_args pba_flags in the case that >MSI-X is supported, and then the MD code will filter it out:
I traced through what one of my non-MSI machines does at boot. The wm(4) driver asks for MSI-X interrupts, the MD PCI code gives it an INTx interrupt, the driver sets things up correctly to use the returned interrupt, it doesn't loop in the driver retrying the pci_intr_alloc().
