linux-kernel - Re: [patch 00/37] genirq/msi, PCI/MSI: Spring cleaning

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Date:   Sat, 27 Nov 2021 20:39:05 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Marc Zygnier <maz@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        iommu@...ts.linux-foundation.org, dmaengine@...r.kernel.org,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, x86@...nel.org,
        Vinod Koul <vkoul@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>, Sinan Kaya <okaya@...nel.org>
Subject: Re: [patch 00/37] genirq/msi, PCI/MSI: Spring cleaning - Part 2

On Sat, Nov 27, 2021 at 02:21:17AM +0100, Thomas Gleixner wrote:
> This is the second part of [PCI]MSI refactoring which aims to provide the
> ability of expanding MSI-X vectors after enabling MSI-X.
> 
> The first part of this work can be found here:
> 
>     https://lore.kernel.org/r/20211126222700.862407977@linutronix.de
> 
> This second part has the following important changes:
> 
>    1) Cleanup of the MSI related data in struct device
> 
>       struct device contains at the moment various MSI related parts. Some
>       of them (the irq domain pointer) cannot be moved out, but the rest
>       can be allocated on first use. This is in preparation of adding more
>       per device MSI data later on.
> 
>    2) Consolidation of sysfs handling
> 
>       As a first step this moves the sysfs pointer from struct msi_desc
>       into the new per device MSI data structure where it belongs.
> 
>       Later changes will cleanup this code further, but that's not possible
>       at this point.
> 
>    3) Store per device properties in the per device MSI data to avoid
>       looking up MSI descriptors and analysing their data. Cleanup all
>       related use cases.
> 
>    4) Provide a function to retrieve the Linux interrupt number for a given
>       MSI index similar to pci_irq_vector() and cleanup all open coded
>       variants.

The msi_get_virq() sure does make a big difference.. Though it does
highlight there is some asymmetry with how platform and PCI works here
where PCI fills some 'struct msix_entry *'. Many drivers would be
quite happy to just call msi_get_virq() and avoid the extra memory, so
I think the msi_get_virq() version is good.

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

Thanks,
Jason