Re: [PATCH RFC v2 04/18] irq/dev-msi: Introduce APIs to allocate/free dev-msi interrupts

[Dey, Megha]

On 7/21/2020 9:25 AM, Jason Gunthorpe wrote:
> On Tue, Jul 21, 2020 at 09:02:41AM -0700, Dave Jiang wrote:
> > From: Megha Dey <megha.dey@xxxxxxxxx>
> >
> > The dev-msi interrupts are to be allocated/freed only for custom devices,
> > not standard PCI-MSIX devices.
> >
> > These interrupts are device-defined and they are distinct from the already
> > existing msi interrupts:
> > pci-msi: Standard PCI MSI/MSI-X setup format
> > platform-msi: Platform custom, but device-driver opaque MSI setup/control
> > arch-msi: fallback for devices not assigned to the generic PCI domain
> > dev-msi: device defined IRQ domain for ancillary devices. For e.g. DSA
> > portal devices use device specific IMS(Interrupt message store) interrupts.
> >
> > dev-msi interrupts are represented by their own device-type. That means
> > dev->msi_list is never contended for different interrupt types. It
> > will either be all PCI-MSI or all device-defined.
>
> Not sure I follow this, where is the enforcement that only dev-msi or
> normal MSI is being used at one time on a single struct device?

So, in the dev_msi_alloc_irqs, I first check if the dev_is_pci..
If it is a pci device, it is forbidden to use dev-msi and must use the 
pci subsystem calls. dev-msi is to be used for all other custom devices, 
mdev or otherwise.

> Jason