linux-kernel - Re: [PATCH] PCI: Relax function 0 VPD test and relocate

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Date:	Wed, 23 Sep 2015 11:20:37 -0600
From:	Myron Stowe <myron.stowe@...il.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	linux-pci <linux-pci@...r.kernel.org>, mark.d.rustad@...el.com,
	Myron Stowe <myron.stowe@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: Relax function 0 VPD test and relocate

On Tue, Sep 15, 2015 at 10:24 PM, Alex Williamson
<alex.williamson@...hat.com> wrote:
> When we quirk a device with PCI_DEV_FLAGS_VPD_REF_F0 we're expecting
> to find a device where all the functions are identical.  If we don't
> find that, we don't make VPD accessible through pci_vpd_ops.  That
> means that if we quirk devices we shouldn't, we filter them out by
> hiding VPD entirely rather than allowing default access.  Instead, we
> can flip this around to only quirk devices that match a slightly more
> rigorous test in the quirk, allowing regular access for anything else.
>
> Tests for the multifunction flag are removed since a) function 0 and
> the function under test are clearly a multifunction device if we're
> scanning a non-zero function in the same slot and b) at this point the
> flag is only set in the device under test if the multifunction bit is
> set in the PCI HEADER, which is a point of interpretation for the PCI
> spec.
>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>
> This is potentially another stable candiate since we're continuing to
> iterate on 932c435caba8, but since we don't actually know of a device
> where VPD is blocked (we don't think my Skylake example actually
> supports VPD), I'm not including it.  I would support it if requested
> though.
>
>  drivers/pci/access.c |   22 ----------------------
>  drivers/pci/quirks.c |   20 ++++++++++++++++++--
>  2 files changed, 18 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> index 5a5f0a7..59ac36f 100644
> --- a/drivers/pci/access.c
> +++ b/drivers/pci/access.c
> @@ -475,23 +475,6 @@ static const struct pci_vpd_ops pci_vpd_f0_ops = {
>         .release = pci_vpd_pci22_release,
>  };
>
> -static int pci_vpd_f0_dev_check(struct pci_dev *dev)
> -{
> -       struct pci_dev *tdev = pci_get_slot(dev->bus,
> -                                           PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
> -       int ret = 0;
> -
> -       if (!tdev)
> -               return -ENODEV;
> -       if (!tdev->vpd || !tdev->multifunction ||
> -           dev->class != tdev->class || dev->vendor != tdev->vendor ||
> -           dev->device != tdev->device)
> -               ret = -ENODEV;
> -
> -       pci_dev_put(tdev);
> -       return ret;
> -}
> -
>  int pci_vpd_pci22_init(struct pci_dev *dev)
>  {
>         struct pci_vpd_pci22 *vpd;
> @@ -500,12 +483,7 @@ int pci_vpd_pci22_init(struct pci_dev *dev)
>         cap = pci_find_capability(dev, PCI_CAP_ID_VPD);
>         if (!cap)
>                 return -ENODEV;
> -       if (dev->dev_flags & PCI_DEV_FLAGS_VPD_REF_F0) {
> -               int ret = pci_vpd_f0_dev_check(dev);
>
> -               if (ret)
> -                       return ret;
> -       }
>         vpd = kzalloc(sizeof(*vpd), GFP_ATOMIC);
>         if (!vpd)
>                 return -ENOMEM;
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 6a30252..b03373f 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -1907,11 +1907,27 @@ static void quirk_netmos(struct pci_dev *dev)
>  DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_NETMOS, PCI_ANY_ID,
>                          PCI_CLASS_COMMUNICATION_SERIAL, 8, quirk_netmos);
>
> +/*
> + * Quirk non-zero PCI functions to route VPD access through function 0 for
> + * devices that share VPD resources between functions.  The functions are
> + * expected to be identical devices.
> + */
>  static void quirk_f0_vpd_link(struct pci_dev *dev)
>  {
> -       if (!dev->multifunction || !PCI_FUNC(dev->devfn))
> +       struct pci_dev *f0;
> +
> +       if (!PCI_FUNC(dev->devfn))
>                 return;
> -       dev->dev_flags |= PCI_DEV_FLAGS_VPD_REF_F0;
> +
> +       f0 = pci_get_slot(dev->bus, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
> +       if (!f0)
> +               return;
> +
> +       if (f0->vpd && dev->class == f0->class &&
> +           dev->vendor == f0->vendor && dev->device == f0->device)
> +               dev->dev_flags |= PCI_DEV_FLAGS_VPD_REF_F0;
> +
> +       pci_dev_put(f0);
>  }
>  DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_INTEL, PCI_ANY_ID,
>                               PCI_CLASS_NETWORK_ETHERNET, 8, quirk_f0_vpd_link);
>
> --
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Acked-by: Myron Stowe <myron.stowe@...hat.com>
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