linux-kernel - Re: [patch V2 25/36] PCI/MSI: Provide MSI_FLAG_MSIX

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Message-ID: <20211207210522.GA77919@bhelgaas>
Date:   Tue, 7 Dec 2021 15:05:22 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        Cedric Le Goater <clg@...d.org>,
        xen-devel@...ts.xenproject.org, Juergen Gross <jgross@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Will Deacon <will@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        iommu@...ts.linux-foundation.org, dmaengine@...r.kernel.org,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Vinod Koul <vkoul@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Robin Murphy <robin.murphy@....com>,
        Sinan Kaya <okaya@...nel.org>
Subject: Re: [patch V2 25/36] PCI/MSI: Provide MSI_FLAG_MSIX_CONTIGUOUS

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@...utronix.de>
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  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,
>