Re: [patch V2 24/46] PCI: vmd: Mark VMD irqdomain with DOMAIN_BUS_VMD_MSI

[Jason Gunthorpe]

On Wed, Aug 26, 2020 at 01:16:52PM +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> 
> Devices on the VMD bus use their own MSI irq domain, but it is not
> distinguishable from regular PCI/MSI irq domains. This is required
> to exclude VMD devices from getting the irq domain pointer set by
> interrupt remapping.
> 
> Override the default bus token.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>  drivers/pci/controller/vmd.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> +++ b/drivers/pci/controller/vmd.c
> @@ -579,6 +579,12 @@ static int vmd_enable_domain(struct vmd_
>  		return -ENODEV;
>  	}
>  
> +	/*
> +	 * Override the irq domain bus token so the domain can be distinguished
> +	 * from a regular PCI/MSI domain.
> +	 */
> +	irq_domain_update_bus_token(vmd->irq_domain, DOMAIN_BUS_VMD_MSI);
> +

Having the non-transparent-bridge hold a MSI table and
multiplex/de-multiplex IRQs looks like another good use case for
something close to pci_subdevice_msi_create_irq_domain()?

If each device could have its own internal MSI-X table programmed
properly things would work alot better. Disable capture/remap of the
MSI range in the NTB.

Then each device could have a proper non-multiplexed interrupt
delivered to the CPU.. Affinity would work properly, no need to share
IRQs (eg vmd_irq() goes away)/etc.

Something for the VMD maintainers to think about at least.

As I hear more about NTB these days a full MSI scheme for NTB seems
interesting to have in the PCI-E core code..

Jason