Re: [PATCH v3 0/4] vfio: selftests: update DMA mapping tests to use queried IOVA ranges

[Alex Mastro <amastro@fb.com>]

On Wed, Nov 12, 2025 at 09:51:35AM -0800, David Matlack wrote:
> On Wed, Nov 12, 2025 at 9:40 AM Alex Mastro <amastro@fb.com> wrote:
> >
> > Hey David, is vfio_pci_driver_test known to be in good shape? Both on the base
> > commit and after my series, I am seeing below, which results in a KSFT_SKIP.
> > Invoking other tests in a similar way actually runs things with expected
> > results (my devices are already bound to vfio-pci before running anything).
> >
> > base commit: 0ed3a30fd996cb0cac872432cf25185fda7e5316
> >
> > $ vfio_pci_driver_test -f 0000:05:00.0
> > No driver found for device 0000:05:00.0
> >
> > Same thing using the run.sh wrapper
> >
> > $ sudo ./run.sh -d 0000:05:00.0 ./vfio_pci_driver_test
> > + echo "0000:05:00.0" > /sys/bus/pci/drivers/vfio-pci/unbind
> > + echo "vfio-pci" > /sys/bus/pci/devices/0000:05:00.0/driver_override
> > + echo "0000:05:00.0" > /sys/bus/pci/drivers/vfio-pci/bind
> >
> > No driver found for device 0000:05:00.0
> > + echo "0000:05:00.0" > /sys/bus/pci/drivers/vfio-pci/unbind
> > + echo "" > /sys/bus/pci/devices/0000:05:00.0/driver_override
> > + echo "0000:05:00.0" > /sys/bus/pci/drivers/vfio-pci/bind
> >
> > device = vfio_pci_device_init(device_bdf, default_iommu_mode);
> > if (!device->driver.ops) {
> >         fprintf(stderr, "No driver found for device %s\n", device_bdf);
> >         return KSFT_SKIP;
> > }
> >
> > Is this meant to be a placeholder for some future testing, or am I holding
> > things wrong?
> 
> What kind of device are you using?
> 
> This test uses the selftests driver framework, so it requires a driver
> in tools/testing/selftests/vfio/lib/drivers to function. The driver
> framework allows tests to trigger real DMA and MSIs from the device in
> a controlled, generic, way.

Ah, TIL about that concept. This is with one of our internal compute
accelerators, so not surprising that I'm seeing a skip then.

> We currently only have drivers for Intel DSA and Intel CBDMA
> devices.So if you're not using one of those devices,
> vfio_pci_driver_test exiting with KSFT_SKIP is entirely expected.
> 
> I would love to add support for more devices. Jason Gunthrope
> suggested supporting a driver for mlx5 class hardware, since it's
> broadly available. I've also had some discussions about adding a
> simple emulated PCIe device to QEMU for running VFIO selftests within
> VMs.

I do have access to mlx5 hardware FWIW, so that would be cool.

Thanks for the explanation!

Alex