linux-kernel - RE: [patch V2 25/33] PCI/MSI: Provide post-enable dynamic allocation interfaces for MSI-X

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Date:   Thu, 24 Nov 2022 02:58:38 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
CC:     "x86@...nel.org" <x86@...nel.org>, Joerg Roedel <joro@...tes.org>,
        "Will Deacon" <will@...nel.org>,
        "linux-pci@...r.kernel.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>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        "Raj, Ashok" <ashok.raj@...el.com>, Jon Mason <jdmason@...zu.us>,
        Allen Hubbe <allenbh@...il.com>
Subject: RE: [patch V2 25/33] PCI/MSI: Provide post-enable dynamic allocation
 interfaces for MSI-X

> From: Thomas Gleixner <tglx@...utronix.de>
> Sent: Monday, November 21, 2022 10:38 PM
> 
> +/**
> + * pci_msix_alloc_irq_at - Allocate an MSI-X interrupt after enabling MSI-X
> + *			   at a given MSI-X vector index or any free vector
> index
> + *
> + * @dev:	PCI device to operate on
> + * @index:	Index to allocate. If @index == MSI_ANY_INDEX this allocates
> + *		the next free index in the MSI-X table

%MSI_ANY_INDEX as done in other places.

> +
> +/**
> + * pci_msix_free_irq - Free an interrupt on a PCI/MSIX interrupt domain
> + *		      which was allocated via pci_msix_alloc_irq_at()
> + *
> + * @dev:	The PCI device to operate on
> + * @map:	A struct msi_map describing the interrupt to free
> + *		as returned from the allocation function.
> + */

Can this be used on preallocated descriptors? If not any guard required
or just treat it as a driver responsibility to not misuse?

> +void pci_msix_free_irq(struct pci_dev *dev, struct msi_map map)
> +{
> +	if (WARN_ON_ONCE(map.index < 0 || map.virq <= 0))

map.virq cannot be negative.