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

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Message-ID: <CALzav=fwE2kPqJUiB2J20pK5bH_-1XvONQXz1DpsMSOCKa=X+g@mail.gmail.com>
Date: Wed, 12 Nov 2025 09:51:35 -0800
From: David Matlack <dmatlack@...gle.com>
To: Alex Mastro <amastro@...com>
Cc: Alex Williamson <alex@...zbot.org>, Shuah Khan <shuah@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>, 
	kvm@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/4] vfio: selftests: update DMA mapping tests to use
 queried IOVA ranges

On Wed, Nov 12, 2025 at 9:40 AM Alex Mastro <amastro@...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.

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.