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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     "Tian, Kevin" <kevin.tian@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "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>,
        "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 27/33] genirq/msi: Provide constants for PCI/IMS support
In-Reply-To: <Y39tCFWB7I/fFEAa@nvidia.com>
References: <20221121083657.157152924@linutronix.de>
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 <BN9PR11MB5276C9AE570B4CF854F6F5E48C0F9@BN9PR11MB5276.namprd11.prod.outlook.com>
 <87o7swd8gi.ffs@tglx> <Y39tCFWB7I/fFEAa@nvidia.com>
Date:   Thu, 24 Nov 2022 14:28:30 +0100
Message-ID: <875yf4cwht.ffs@tglx>
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On Thu, Nov 24 2022 at 09:09, Jason Gunthorpe wrote:
> On Thu, Nov 24, 2022 at 10:10:05AM +0100, Thomas Gleixner wrote:
>> On Thu, Nov 24 2022 at 03:01, Kevin Tian wrote:
>> > SECONDARY or be explicit IMS? Are we envisioning non-IMS usages to
>> > occupy this slot in the future?
>> 
>> I'm not really decided on that. Whatever the name or use-case for a
>> secondary domain is. Not, that this is not restricted to PCI.
>
> This is hierarchical right? So if a pci_device spawns an
> auxiliary_device, its driver could stick a msi domain on the
> MSI_DEFAULT_DOMAIN of the aux device as a child of the PCI device's
> domain?

A child of the PCI devices parent domain. The per device domains are
endpoint domains. They cannot serve as parent domains themself right
now.

If there is a real reason and use case which requires that, it can be
made work with trivial tweaks.

Thanks,

        tglx