KVM: selftests: Add VFIO device support to eventfd IRQ test

Extend the eventfd IRQ test with a '-d' argument that takes a BDF (in the
format segment:bus:device.function) of an interrupt-capable PCI(e) device
bound to VFIO, and use said device to trigger interrupts instead of always
synthesizing interrupts via direct writes to the eventfd.

Using a VFIO device to trigger interrupts validates the end-to-end delivery
of IRQs for "real" devices, and when supported by hardware (and KVM), also
validates interrupt delivery via IRQ bypass, i.e. via device posted IRQs.

Now that IOMMUFD is a thing, auto-probe IOMMUFD vs. "legacy" VFIO by
temporarily opening /dev/iommufd, and skip the test if neither IOMMUFD nor
legacy VFIO is available.  Add a '-t' option to the user override the probe
logic, e.g. in case IOMMUFD is available but the system is configured for
legacy usage.

Note, the device must have a VFIO selftest driver in order to work with
the test.  A helper script to list supported devices will hopefully be
available in the near future at
tools/testing/selftests/vfio/scripts/list_supported_devices.sh[1].

Example:
$ ./tools/testing/selftests/kvm/irq_test -d 0000:06:0a.1

Link: https://lore.kernel.org/all/20260602222941.3133236-1-jrhilke%40google.com [1]
Signed-off-by: David Matlack <dmatlack@google.com>
Co-developed-by: Josh Hilke <jrhilke@google.com>
Signed-off-by: Josh Hilke <jrhilke@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Link: https://patch.msgid.link/20260626213534.3866178-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

0 files changed, 0 insertions, 0 deletions