Re: [PATCH iommufd 4/9] iommufd: Convert to msi_device_has_secure_msi()

[Thomas Gleixner <tglx@linutronix.de>]

On Mon, Dec 12 2022 at 11:47, Jason Gunthorpe wrote:
> On Mon, Dec 12, 2022 at 04:17:58PM +0100, Thomas Gleixner wrote:
>> Obvioulsy unless it's done somewhere early in the PCI discovery,
>> i.e. before the discovery associated the domain pointer.
>
> I thought the problem is more that the iommu drivers change the
> assigned irq_domain:

Yes they do.

> void intel_irq_remap_add_device(struct dmar_pci_notify_info *info)
> {
> 	if (!irq_remapping_enabled || pci_dev_has_special_msi_domain(info->dev))
> 		return;
>
> 	dev_set_msi_domain(&info->dev->dev, map_dev_to_ir(info->dev));
> }
>
> Which is ultimately called by 
>
> 	bus_register_notifier(&pci_bus_type, &dmar_pci_bus_nb);
>
> And that compares with the iommu setup which is also done from a
> bus notifier:
>
> 		nb[i].notifier_call = iommu_bus_notifier;
> 		bus_register_notifier(iommu_buses[i], &nb[i]);
>
> So, I think, there is not reliable ordering between these two things.

Bah. Notifiers are a complete disaster vs. ordering. This really wants
reliable ordering IMO.

Thanks,

        tglx