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

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Message-ID: <CEE05A0D7856E14880AD5560634EBEA834DB8E96@SFO1EXC-MBXP06.nbttech.com>
Date:	Wed, 12 Sep 2012 01:13:55 +0000
From:	Jiang Wang <Jiang.Wang@...erbed.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chaitanya Lala <Chaitanya.Lala@...erbed.com>,
	"Francis St. Amant" <Francis.St.Amant@...erbed.com>
Subject: RE: [PATCH 1/1] pci-iov: Fix warnings when CONFIG_PCI_IOV is enabled


-----Original Message-----
From: Bjorn Helgaas [mailto:bhelgaas@...gle.com] 
Sent: Tuesday, September 11, 2012 4:35 PM
To: Jiang Wang
Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; Chaitanya Lala; Francis St. Amant; Jiang Wang
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.

--- I see. I didn't find the code in sriov_enable() before I send out the patch. Thanks for the info.

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.

---- My purpose here is to remove those warnings. I also tried to disable CONFIG_PCI_IOV, but that causes another strange problem on one of machines. The LSI controller cannot get memory resources and 32 LSI controllers shown up even though only one actually exist.
I will drop this patch and do more debug to see what that problem is. Thanks.
 
Bjorn

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

Regards,

Jiang
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