Re: [patch 12/33] PCI/MSI: Add support for per device MSI[X] domains

[Jason Gunthorpe]

On Wed, Nov 16, 2022 at 11:38:52PM +0100, Thomas Gleixner wrote:

> >> +bool pci_setup_msi_device_domain(struct pci_dev *pdev)
> >> +{
> >> +	if (WARN_ON_ONCE(pdev->msix_enabled))
> >> +		return false;
> >> +
> >> +	if (pci_match_device_domain(pdev, DOMAIN_BUS_PCI_DEVICE_MSI))
> >> +		return true;
> >> +	if (pci_match_device_domain(pdev, DOMAIN_BUS_PCI_DEVICE_MSIX))
> >> +		msi_remove_device_irq_domain(&pdev->dev, MSI_DEFAULT_DOMAIN);
> >> +
> >> +	return pci_create_device_domain(pdev, &pci_msi_template, 1);
> >
> > Hardwired to one 1? What about multi-msi?
> 
> MSI has exactly ONE descriptor whether it's single or multi-MSI.
> 
> Multi-MSI can have several interrupts hanging off the same descriptor,
> but that's not how MSI looks at it because you write ONE message and the
> hardware does the substitution of the low bits depending on which vector
> is raised.

Okay, that is very clear, maybe this in a comment right here ?

Jason