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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Tian, Kevin" <kevin.tian@intel.com>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     "x86@kernel.org" <x86@kernel.org>, Joerg Roedel <joro@8bytes.org>,
        Will Deacon <will@kernel.org>,
        "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jason Gunthorpe <jgg@mellanox.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        "Raj, Ashok" <ashok.raj@intel.com>, Jon Mason <jdmason@kudzu.us>,
        Allen Hubbe <allenbh@gmail.com>
Subject: RE: [patch V2 25/33] PCI/MSI: Provide post-enable dynamic
 allocation interfaces for MSI-X
In-Reply-To: <BN9PR11MB527668DB0B5B9C8D8C36C95F8C0F9@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20221121083657.157152924@linutronix.de>
 <20221121091327.869774994@linutronix.de>
 <BN9PR11MB527668DB0B5B9C8D8C36C95F8C0F9@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Thu, 24 Nov 2022 10:08:31 +0100
Message-ID: <87r0xsd8j4.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Thu, Nov 24 2022 at 02:58, Kevin Tian wrote:
>> +
>> +/**
>> + * 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?

The preallocated descriptors are only relevant during setup, but not
post setup. So yes, you can do:

pci_alloc_irq_vectors(dev, 10, 10, PCI_IRQ_MSIX);

and then

    map = { .index = 9, .virq = $IRQ };
    pci_msix_free_irq(dev, &map);

It just works.

>> +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.

Why? Callers can make up whatever they want, no?

Thanks,

        tglx