linux-kernel - Re: [patch V4 09-01/35] PCI/MSI: Decouple MSI[-X] disable from pcim

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Date:   Wed, 15 Dec 2021 18:46:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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>,
        Jason Gunthorpe <jgg@...dia.com>,
        Megha Dey <megha.dey@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, linux-pci@...r.kernel.org,
        Cedric Le Goater <clg@...d.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel@...ts.xenproject.org, Arnd Bergmann <arnd@...db.de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org, Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Vinod Koul <vkoul@...nel.org>, dmaengine@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org,
        Jassi Brar <jassisinghbrar@...il.com>,
        Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Sinan Kaya <okaya@...nel.org>
Subject: Re: [patch V4 09-01/35] PCI/MSI: Decouple MSI[-X] disable from
 pcim_release()

On Wed, Dec 15, 2021 at 06:16:44PM +0100, Thomas Gleixner wrote:
> The MSI core will introduce runtime allocation of MSI related data. This
> data will be devres managed and has to be set up before enabling
> PCI/MSI[-X]. This would introduce an ordering issue vs. pcim_release().
> 
> The setup order is:
> 
>    pcim_enable_device()
> 	devres_alloc(pcim_release...);
> 	...
> 	pci_irq_alloc()
> 	  msi_setup_device_data()
> 	     devres_alloc(msi_device_data_release, ...)
> 
> and once the device is released these release functions are invoked in the
> opposite order:
> 
>     msi_device_data_release()
>     ...
>     pcim_release()
>        pci_disable_msi[x]()
> 
> which is obviously wrong, because pci_disable_msi[x]() requires the MSI
> data to be available to tear down the MSI[-X] interrupts.
> 
> Remove the MSI[-X] teardown from pcim_release() and add an explicit action
> to be installed on the attempt of enabling PCI/MSI[-X].
> 
> This allows the MSI core data allocation to be ordered correctly in a
> subsequent step.
> 
> Reported-by: Nishanth Menon <nm@...com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> V4: New patch


Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>