linux-kernel - Re: [patch V2 20/23] PCI/MSI: Move msi_lock to struct pci

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Date:   Wed, 8 Dec 2021 11:29:25 -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,
        Cedric Le Goater <clg@...d.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org, Juergen Gross <jgross@...e.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, Kalle Valo <kvalo@...eaurora.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        sparclinux@...r.kernel.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org, ath11k@...ts.infradead.org,
        Wei Liu <wei.liu@...nel.org>, linux-hyperv@...r.kernel.org,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>
Subject: Re: [patch V2 20/23] PCI/MSI: Move msi_lock to struct pci_dev

On Mon, Dec 06, 2021 at 11:27:56PM +0100, Thomas Gleixner wrote:
> It's only required for PCI/MSI. So no point in having it in every struct
> device.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> V2: New patch
> ---
>  drivers/base/core.c    |    1 -
>  drivers/pci/msi/msi.c  |    2 +-
>  drivers/pci/probe.c    |    4 +++-
>  include/linux/device.h |    2 --
>  include/linux/pci.h    |    1 +
>  5 files changed, 5 insertions(+), 5 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
 
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2875,7 +2875,6 @@ void device_initialize(struct device *de
>  	device_pm_init(dev);
>  	set_dev_node(dev, NUMA_NO_NODE);
>  #ifdef CONFIG_GENERIC_MSI_IRQ
> -	raw_spin_lock_init(&dev->msi_lock);
>  	INIT_LIST_HEAD(&dev->msi_list);
>  #endif
>  	INIT_LIST_HEAD(&dev->links.consumers);
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -18,7 +18,7 @@ int pci_msi_ignore_mask;
>  
>  static noinline void pci_msi_update_mask(struct msi_desc *desc, u32 clear, u32 set)
>  {
> -	raw_spinlock_t *lock = &desc->dev->msi_lock;
> +	raw_spinlock_t *lock = &to_pci_dev(desc->dev)->msi_lock;
>  	unsigned long flags;
>  
>  	if (!desc->pci.msi_attrib.can_mask)

It looks like most of the time this is called by an irq_chip, except
for a few special cases list pci_msi_shutdown()

Is this something that should ideally go away someday and use some
lock in the irq_chip - not unlike what we've thought is needed for
IMS?

Jason