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

[Bjorn Helgaas]

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,
>