linux-kernel - Re: [PATCH] PCI/VFIO: use pcie_flags_reg instead of access PCI-E Capabilities Register

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Date:	Mon, 01 Apr 2013 09:16:01 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Yijing Wang <wangyijing@...wei.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	Hanjun Guo <guohanjun@...wei.com>, jiang.liu@...wei.com
Subject: Re: [PATCH] PCI/VFIO: use pcie_flags_reg instead of access PCI-E
 Capabilities Register

On Wed, 2013-03-27 at 17:05 +0800, Yijing Wang wrote:
> Currently, we use pcie_flags_reg to cache PCI-E Capabilities Register,
> because PCI-E Capabilities Register bits are almost read-only. This patch
> use pcie_flags_reg instead of another access PCI-E Capabilities Register.
> 
> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
> ---
>  drivers/vfio/pci/vfio_pci_config.c |    6 +-----
>  1 files changed, 1 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
> index aeb00fc..afc6ca4 100644
> --- a/drivers/vfio/pci/vfio_pci_config.c
> +++ b/drivers/vfio/pci/vfio_pci_config.c
> @@ -1017,13 +1017,9 @@ static int vfio_cap_len(struct vfio_pci_device *vdev, u8 cap, u8 pos)
>  		return byte;
>  	case PCI_CAP_ID_EXP:
>  		/* length based on version */
> -		ret = pci_read_config_word(pdev, pos + PCI_EXP_FLAGS, &word);
> -		if (ret)
> -			return pcibios_err_to_errno(ret);
> -
>  		vdev->extended_caps = true;
>  
> -		if ((word & PCI_EXP_FLAGS_VERS) == 1)
> +		if ((pdev->pcie_flags_reg & PCI_EXP_FLAGS_VERS) == 1)

It looks like we should be using pcie_caps_reg(pdev) here instead of
directly accessing pcie_flags_reg.  Thanks,

Alex

>  			return PCI_CAP_EXP_ENDPOINT_SIZEOF_V1;
>  		else
>  			return PCI_CAP_EXP_ENDPOINT_SIZEOF_V2;



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