RE: [PATCH 1/1] pci-iov: Fix warnings when CONFIG_PCI_IOV is enabled

From: Jiang Wang
Date: Tue Sep 11 2012 - 21:13:50 EST

-----Original Message-----
From: Bjorn Helgaas [mailto:bhelgaas@xxxxxxxxxx]
Sent: Tuesday, September 11, 2012 4:35 PM
To: Jiang Wang
Cc: linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; 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@xxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> ---
> 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.


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


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