linux-kernel - Re: [PATCH v8 3/4] PCI: Introduce disable_acs

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Message-ID: <20180809211714.GG113140@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 9 Aug 2018 16:17:14 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-doc@...r.kernel.org, Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Christian König <christian.koenig@....com>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v8 3/4] PCI: Introduce disable_acs_redir quirk

On Mon, Jul 30, 2018 at 10:18:39AM -0600, Logan Gunthorpe wrote:
> Intel SPT PCH hardware has an implementation of the ACS bits that
> does not comply with the PCI express standard. To deal with this
> the existing code has an enable_acs() quirk for the hardware.
> 
> In order to be able to correctly disable the ACS redirect bits for
> all hardware we need an analagous quirk to disable those bits.
> 
> This adds the function pci_dev_specific_disable_acs_redir() which
> behaves similarly to pci_dev_specific_enable_acs() but uses a new
> function pointer for quirks which disables the ACS redirect bits.
> 
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Reviewed-by: Alex Williamson <alex.williamson@...hat.com>
> ---
> ...

> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index abd5d5e17aee..0a436ec4fef5 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1880,6 +1880,7 @@ enum pci_fixup_pass {
>  void pci_fixup_device(enum pci_fixup_pass pass, struct pci_dev *dev);
>  int pci_dev_specific_acs_enabled(struct pci_dev *dev, u16 acs_flags);
>  int pci_dev_specific_enable_acs(struct pci_dev *dev);
> +int pci_dev_specific_disable_acs_redir(struct pci_dev *dev);
>  #else
>  static inline void pci_fixup_device(enum pci_fixup_pass pass,
>  				    struct pci_dev *dev) { }
> @@ -1892,6 +1893,10 @@ static inline int pci_dev_specific_enable_acs(struct pci_dev *dev)
>  {
>  	return -ENOTTY;
>  }
> +static inline int pci_dev_specific_disable_acs_redir(struct pci_dev *dev)
> +{
> +	return -ENOTTY;
> +}

I assume these could go in drivers/pci/pci.h instead of
include/linux/pci.h?

I can do that (and add another patch to move the
pci_dev_specific_acs_enabled() and pci_dev_specific_enable_acs()
declarations, which also are only used inside drivers/pci) if you agree.

>  #endif
>  
>  void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen);
> -- 
> 2.11.0
>