Re: [patch V2 25/36] PCI/MSI: Provide MSI_FLAG_MSIX_CONTIGUOUS

[Bjorn Helgaas <helgaas@xxxxxxxxxx>]

On Mon, Dec 06, 2021 at 11:39:36PM +0100, Thomas Gleixner wrote:
> Provide a domain info flag which makes the core code check for a contiguous
> MSI-X index on allocation. That's simpler than checking it at some other
> domain callback in architecture code.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

> ---
>  drivers/pci/msi/irqdomain.c |   16 ++++++++++++++--
>  include/linux/msi.h         |    2 ++
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -89,9 +89,21 @@ static int pci_msi_domain_check_cap(stru
>       if (pci_msi_desc_is_multi_msi(desc) &&
>           !(info->flags & MSI_FLAG_MULTI_PCI_MSI))
>               return 1;
> -     else if (desc->pci.msi_attrib.is_msix && !(info->flags & 
> MSI_FLAG_PCI_MSIX))
> -             return -ENOTSUPP;
>  
> +     if (desc->pci.msi_attrib.is_msix) {
> +             if (!(info->flags & MSI_FLAG_PCI_MSIX))
> +                     return -ENOTSUPP;
> +
> +             if (info->flags & MSI_FLAG_MSIX_CONTIGUOUS) {
> +                     unsigned int idx = 0;
> +
> +                     /* Check for gaps in the entry indices */
> +                     for_each_msi_entry(desc, dev) {
> +                             if (desc->msi_index != idx++)
> +                                     return -ENOTSUPP;
> +                     }
> +             }
> +     }
>       return 0;
>  }
>  
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -376,6 +376,8 @@ enum {
>       MSI_FLAG_LEVEL_CAPABLE          = (1 << 6),
>       /* Populate sysfs on alloc() and destroy it on free() */
>       MSI_FLAG_DEV_SYSFS              = (1 << 7),
> +     /* MSI-X entries must be contiguous */
> +     MSI_FLAG_MSIX_CONTIGUOUS        = (1 << 8),
>  };
>  
>  int msi_domain_set_affinity(struct irq_data *data, const struct cpumask 
> *mask,
>