Re: [PATCH 04/17] gpu: nova-core: allocate PCI MSI vector during probe

["Danilo Krummrich" <dakr@kernel.org>]

On Sat Aug 8, 2026 at 5:11 AM CEST, John Hubbard wrote:
> Allocate a single PCI MSI interrupt vector in the probe path.
>
> Try MSI/MSI-X first. If that fails (possible in broken VFIO setups),
> fall back to INTx with a dev_warn so the issue is visible in dmesg.
> The allocation is devres-managed and automatically freed on unbind.

[...]

> +pub(crate) fn alloc_vector(pdev: &pci::Device<Bound>) -> Result<pci::IrqVector<'_>> {
> +    let msi_types = IrqTypes::default().with(IrqType::Msi).with(IrqType::MsiX);

I was about to ask if we really need to bother with MSI and shouln't just go for
MSI-X only.

But then saw that the commit message mentions broken VFIO setups; can you expand
on this a bit? Which setups is the commit message referring to?

> +
> +    let irq_vectors = match pdev.alloc_irq_vectors(1, 1, msi_types) {
> +        Ok(vecs) => vecs,
> +        Err(_) => {
> +            dev_warn!(pdev.as_ref(), "MSI not available, falling back to INTx\n");
> +            pdev.alloc_irq_vectors(1, 1, IrqTypes::default().with(IrqType::Intx))?
> +        }
> +    };
> +
> +    irq_vectors.vector(0)
> +}