Re: [PATCH v2 00/14] KVM: selftests: Link with VFIO selftests lib and test device interrupts

[Sean Christopherson <seanjc@google.com>]

On Tue, Mar 31, 2026, Josh Hilke wrote:
> I am taking over development of this series from David Matlack. 
> v1: https://lore.kernel.org/kvm/20250912222525.2515416-1-dmatlack@google.com/
> 
> This series is based on the kvm-upstream/queue branch.
> 
> This series introduces vfio_pci_irq_test, which exercises the delivery
> of VFIO device interrupts (MSI/MSI-X) to guest vCPUs, and links the
> VFIO selftests library into KVM selftests to enable testing of VFIO-KVM
> interactions.
> 
> The test requires a PCI device bound to vfio-pci. It can be invoked by
> passing the BDF the VFIO selftests setup script,

-ENOPARSE

> and then running the test with the device BDF:
> 
>   $ ./tools/testing/selftests/vfio/scripts/setup.sh 0000:6a:01.0

IIUC, what this is saying is that to run the test, the device needs to be bound
to VFIO, and _one_ way to do that is to use ./tools/testing/selftests/vfio/scripts/setup.sh
to do the heavy lifting.

>   $ tools/testing/selftests/kvm/vfio_pci_irq_test 0000:6a:01.0
> 
> This test only supports x86. Testing physical device interrupts (-d argument) is
> only supported for Intel because there are no VFIO selftest drivers for AMD
> devices.

This needs to be expressed in code and human readable error messages to the user.
I already knew the basic of what the VFIO selfests are doing, and it still took
me 5+ minutes to find the DSA driver and probing logic.

Concretely, this code needs to be part of the standard vfio selftests APIs:

	device = vfio_pci_device_init(device_bdf, iommu);

	has_driver = !!device->driver.ops;

E.g. have vfio_pci_device_init() explicitly return an error (or NULL) if it can't
init the device driver.

The fixtures in vfio_pci_driver_test.c already blindly assume success, so you
might not need to do much beyond changing main() in that file.

And then, also as a vfio_pci_device_xxx() API, add a helper to print out what
devices are supported, e.g. so that KVM selftests can do something like:

struct vfio_pci_device *kvm_vfio_device_init(const char *bdf)
{
	struct vfio_pci_device *device;
	struct iommu *iommu;

	iommu = iommu_init(default_iommu_mode);

	device = vfio_pci_device_init(bdf, iommu);
	if (!device) {
		vfio_pci_device_print_drivers(stderr);
		TEST_FAIL("No driver found for BDF '%s'", bdf);
	}
	return device;
}

Because as is, this requires way too much a priori knowledge and magic for
upstream.  The user shouldn't have to dig through code just to understand what
devices are supported.

Ideally, VFIO selftests would also provide a script, utility, and/or helper to
identify BDFs for devices it has drivers for.  In my experience, binding a device
to VFIO is trivial.  Finding the device in the first place is more annoying.

> David Matlack (11):
>   KVM: selftests: Build and link sefltests/vfio/lib into KVM selftests
>   KVM: selftests: Add vfio_pci_irq_test

Make this one human friendly, e.g.

 KVM: selftests: Add a test to verify IRQ delivery from assigned VFIO devices

>   KVM: selftests: Add support for random host IRQ affinity
>   KVM: selftests: Allow blocking vCPUs via HLT
>   KVM: selftests: Add support for physical device MSI triggers
>   KVM: selftests: Add option to clear GSI routes
>   KVM: selftests: Make test IRQ count configurable
>   KVM: selftests: Add support for NMI delivery
>   KVM: selftests: Add support for vCPU pinning
>   KVM: selftests: Support testing with multiple vCPUs
>   KVM: selftests: Add xAPIC mode support

And then for these shortlog, explicitly call out what test they are changing.
The "Allow blocking vCPUs via HLT" shortlog in particular was super confusing.
E.g.

 KVM: selftests: Extend VFIO IRQ test to validate waking vCPU from HLT

> Josh Hilke (3):
>   KVM: selftests: Add helper functions for IRQ testing
>   KVM: selftests: Reproduce tests that rely on randomization

Please post this as a separate, standalone patch.  It's a fix that isn't dependent
on this series in any way.

>   KVM: selftests: Make vfio_pci_irq_test timeout configurable