linux-kernel - Re: [patch 29/33] PCI/MSI: Provide pci_ims_alloc/free

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Date:   Wed, 16 Nov 2022 14:14:46 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Marc Zyngier <maz@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Ashok Raj <ashok.raj@...el.com>, Jon Mason <jdmason@...zu.us>,
        Allen Hubbe <allenbh@...il.com>,
        "Ahmed S. Darwish" <darwi@...utronix.de>,
        Reinette Chatre <reinette.chatre@...el.com>
Subject: Re: [patch 29/33] PCI/MSI: Provide pci_ims_alloc/free_irq()

On Fri, Nov 11, 2022 at 02:58:57PM +0100, Thomas Gleixner wrote:
> Single vector allocation which allocates the next free index in the IMS
> space. The free function releases.
> 
> All allocated vectors are released also via pci_free_vectors() which is
> also releasing MSI/MSI-X vectors.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

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

I would probably capitalize "ID" in the function comment below, but
either way.

> ---
>  drivers/pci/msi/api.c |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pci.h   |    3 +++
>  2 files changed, 53 insertions(+)
> 
> --- a/drivers/pci/msi/api.c
> +++ b/drivers/pci/msi/api.c
> @@ -361,6 +361,56 @@ const struct cpumask *pci_irq_get_affini
>  EXPORT_SYMBOL(pci_irq_get_affinity);
>  
>  /**
> + * pci_ims_alloc_irq - Allocate an interrupt on a PCI/IMS interrupt domain
> + * @dev:	The PCI device to operate on
> + * @cookie:	Pointer to an IMS implementation specific device cookie
> + *		(PASID, queue id, pointer...). The cookie content is stored
> + *		in the MSI descriptor for the interrupt chip callbacks or
> + *		domain specific setup functions
> + * @affdesc:	Optional pointer to an interrupt affinity descriptor
> + *
> + * Return: A struct msi_map
> + *
> + *	On success msi_map::index contains the allocated index (>= 0) and
> + *	msi_map::virq the allocated Linux interrupt number (> 0).
> + *
> + *	On fail msi_map::index contains the error code and msi_map::virq
> + *	is set to 0.
> + *
> + * Note: There is no index for IMS allocations as IMS is an implementation
> + *	 specific storage and does not have any direct associations between
> + *	 index, which might be a pure software construct, and device
> + *	 functionality. This association is established by the driver either
> + *	 via the index - if there is a hardware table - or in case of purely
> + *	 software managed IMS implementation the association happens via
> + *	 the irq_write_msi_msg() callback of the implementation specific
> + *	 interrupt chip, which utilizes the provided @cookie to store the MSI
> + *	 message in the appropriate place.
> + */
> +struct msi_map pci_ims_alloc_irq(struct pci_dev *dev, union msi_dev_cookie *cookie,
> +				 const struct irq_affinity_desc *affdesc)
> +{
> +	return msi_domain_alloc_irq_at(&dev->dev, MSI_SECONDARY_DOMAIN, MSI_ANY_INDEX,
> +				       affdesc, cookie);
> +}
> +EXPORT_SYMBOL_GPL(pci_ims_alloc_irq);
> +
> +/**
> + * pci_ims_free_irq - Allocate an interrupt on a PCI/IMS interrupt domain
> + *		      which was allocated via pci_ims_alloc_irq()
> + * @dev:	The PCI device to operate on
> + * @map:	A struct msi_map describing the interrupt to free as
> + *		returned from pci_ims_alloc_irq()
> + */
> +void pci_ims_free_irq(struct pci_dev *dev, struct msi_map map)
> +{
> +	if (WARN_ON_ONCE(map.index < 0 || !map.virq))
> +		return;
> +	msi_domain_free_irqs_range(&dev->dev, MSI_SECONDARY_DOMAIN, map.index, map.index);
> +}
> +EXPORT_SYMBOL_GPL(pci_ims_free_irq);
> +
> +/**
>   * pci_free_irq_vectors() - Free previously allocated IRQs for a device
>   * @dev: the PCI device to operate on
>   *
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2485,6 +2485,9 @@ struct msi_domain_template;
>  
>  bool pci_create_ims_domain(struct pci_dev *pdev, const struct msi_domain_template *template,
>  			   unsigned int hwsize, void *data);
> +struct msi_map pci_ims_alloc_irq(struct pci_dev *pdev, union msi_dev_cookie *cookie,
> +				 const struct irq_affinity_desc *affdesc);
> +void pci_ims_free_irq(struct pci_dev *pdev, struct msi_map map);
>  
>  #include <linux/dma-mapping.h>
>  
>