Re: [PATCH v6 4/5] [FUTURE] xen/arm: enable vPCI for domUs

["Roger Pau Monné" <roger.pau@citrix.com>]

On Mon, Nov 13, 2023 at 05:21:13PM -0500, Stewart Hildebrand wrote:
> @@ -1618,6 +1630,14 @@ int iommu_do_pci_domctl(
>          bus = PCI_BUS(machine_sbdf);
>          devfn = PCI_DEVFN(machine_sbdf);
>  
> +        if ( needs_vpci(d) && !has_vpci(d) )
> +        {
> +            printk(XENLOG_G_WARNING "Cannot assign %pp to %pd: vPCI support not enabled\n",
> +                   &PCI_SBDF(seg, bus, devfn), d);
> +            ret = -EPERM;
> +            break;

I think this is likely too restrictive going forward.  The current
approach is indeed to enable vPCI on a per-domain basis because that's
how PVH dom0 uses it, due to being unable to use ioreq servers.

If we start to expose vPCI suport to guests the interface should be on
a per-device basis, so that vPCI could be enabled for some devices,
while others could still be handled by ioreq servers.

We might want to add a new flag to xen_domctl_assign_device (used by
XEN_DOMCTL_assign_device) in order to signal whether the device will
use vPCI.

Thanks, Roger.