linux-kernel - Re: [PATCH 1/1] pci-iov: Fix warnings when CONFIG_PCI

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Message-ID: <CAErSpo7vu0uS=06Dr82-LZ3KBzxaje6fV+H=Foi-bD1c6mUcFA@mail.gmail.com>
Date:	Tue, 11 Sep 2012 17:35:11 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiang Wang <Jiang.Wang@...erbed.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	clala@...erbed.com, Francis.St.Amant@...erbed.com,
	Jiang Wang <jwang@...erbed.com>
Subject: Re: [PATCH 1/1] pci-iov: Fix warnings when CONFIG_PCI_IOV is enabled

On Tue, Sep 4, 2012 at 5:11 PM, Jiang Wang <Jiang.Wang@...erbed.com> wrote:
> When CONFIG_PCI_IOV is enabled, the kernel will call sriov_init().
> This function tries to allocate virtual resources even if the
> virtual function of a PCI devive is not enabled by the BIOS.
>
> This sometimes causes following warning messages during boot up:
> pci 0000:02:00.0: BAR 9: can't allocate mem resource [0x000000-0x3fffff]
> pci 0000:02:00.0: BAR 7: can't allocate mem resource [0x000000-0x03ffff]
>
> Tested on three Mitac motherboards.
>
> Signed-off-by: Jiang Wang <jwang@...erbed.com>
> ---
>  drivers/pci/iov.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 6554e1a..0ca8cb2 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -441,7 +441,8 @@ static int sriov_init(struct pci_dev *dev, int pos)
>         if (ctrl & PCI_SRIOV_CTRL_VFE) {
>                 pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, 0);
>                 ssleep(1);
> -       }
> +       } else
> +               return 0;

But this would mean that Linux can't *ever* enable VFs unless the BIOS
enabled them, right?  I don't think that's what we want -- there's
code in sriov_enable() to turn on VFE, assuming we have enough
resources for the VFs.

It's certainly possible that the BIOS didn't allocate large enough
apertures in the bridges leading to the SR-IOV device to accommodate
all the VFs, and Linux may not be smart enough to enlarge them.  And
probably our warning messages in that case are not very enlightening.

Bjorn

>         pci_read_config_word(dev, pos + PCI_SRIOV_TOTAL_VF, &total);
>         if (!total)
> --
> 1.7.1
>
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