linux-kernel - Re: [patch 34/39] PCI/MSI: Reject multi-MSI early

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Message-ID: <Y3Uk8lKAgKU5a63r@nvidia.com>
Date:   Wed, 16 Nov 2022 13:59:14 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
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>,
        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>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linuxppc-dev@...ts.ozlabs.org,
        "Ahmed S. Darwish" <darwi@...utronix.de>,
        Reinette Chatre <reinette.chatre@...el.com>
Subject: Re: [patch 34/39] PCI/MSI: Reject multi-MSI early

On Fri, Nov 11, 2022 at 02:55:09PM +0100, Thomas Gleixner wrote:
> When hierarchical MSI interrupt domains are enabled then there is no point
> to do tons of work and detect the missing support for multi-MSI late in the
> allocation path.
> 
> Just query the domain feature flags right away. The query function is going
> to be used for other purposes later and has a mode argument which influences
> the result:
> 
>   ALLOW_LEGACY returns true when:
>      - there is no irq domain attached (legacy support)
>      - there is a irq domain attached which has the feature flag set
> 
>   DENY_LEGACY returns only true when:
>      - there is a irq domain attached which has the feature flag set
> 
> This allows to use the function universally without ifdeffery in the
> calling code.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  drivers/pci/msi/irqdomain.c |   22 ++++++++++++++++++++++
>  drivers/pci/msi/msi.c       |    4 ++++
>  drivers/pci/msi/msi.h       |    9 +++++++++
>  3 files changed, 35 insertions(+)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason