Re: [patch RFC 21/38] PCI: MSI: Provide pci_dev_has_special_msi_domain() helper

[Bjorn Helgaas <helgaas@xxxxxxxxxx>]

On Fri, Aug 21, 2020 at 02:24:45AM +0200, Thomas Gleixner wrote:
> Provide a helper function to check whether a PCI device is handled by a
> non-standard PCI/MSI domain. This will be used to exclude such devices
> which hang of a special bus, e.g. VMD, to be excluded from the irq domain
> override in irq remapping.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: linux-pci@xxxxxxxxxxxxxxx

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

s|PCI: MSI:|PCI/MSI:| in the subject if feasible.

> ---
>  drivers/pci/msi.c   |   22 ++++++++++++++++++++++
>  include/linux/msi.h |    1 +
>  2 files changed, 23 insertions(+)
> 
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1553,4 +1553,26 @@ struct irq_domain *pci_msi_get_device_do
>                                            DOMAIN_BUS_PCI_MSI);
>       return dom;
>  }
> +
> +/**
> + * pci_dev_has_special_msi_domain - Check whether the device is handled by
> + *                               a non-standard PCI-MSI domain
> + * @pdev:    The PCI device to check.
> + *
> + * Returns: True if the device irqdomain or the bus irqdomain is
> + * non-standard PCI/MSI.
> + */
> +bool pci_dev_has_special_msi_domain(struct pci_dev *pdev)
> +{
> +     struct irq_domain *dom = dev_get_msi_domain(&pdev->dev);
> +
> +     if (!dom)
> +             dom = dev_get_msi_domain(&pdev->bus->dev);
> +
> +     if (!dom)
> +             return true;
> +
> +     return dom->bus_token != DOMAIN_BUS_PCI_MSI;
> +}
> +
>  #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -374,6 +374,7 @@ int pci_msi_domain_check_cap(struct irq_
>                            struct msi_domain_info *info, struct device *dev);
>  u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev 
> *pdev);
>  struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
> +bool pci_dev_has_special_msi_domain(struct pci_dev *pdev);
>  #else
>  static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev 
> *pdev)
>  {
>