linux-kernel - Re: [PATCH] x86/pci/mrst: add extra check in fixed bar detection

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Message-ID: <20100716121248.0f3daa3b@virtuousgeek.org>
Date:	Fri, 16 Jul 2010 12:12:48 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Ben Greear <greearb@...delatech.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/pci/mrst: add extra check in fixed bar detection

On Fri, 16 Jul 2010 11:58:26 -0700
Jacob Pan <jacob.jun.pan@...ux.intel.com> wrote:

> Fixed bar capability structure is searched in PCI extended configuration
> space. We need to make sure there is a valid capability id to begin with
> otherwise, the search code may stuck in a infinite loop which results in
> boot hang.
> This patch adds additional check for cap ID 0, which is also invalid.
> 
> Suggested-by: "H. Peter Anvin" <hpa@...or.com>
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>  arch/x86/pci/mrst.c |    7 ++++---
>  1 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/pci/mrst.c b/arch/x86/pci/mrst.c
> index c9649d0..8636567 100644
> --- a/arch/x86/pci/mrst.c
> +++ b/arch/x86/pci/mrst.c
> @@ -66,8 +66,9 @@ static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn)
>  					  devfn, pos, 4, &pcie_cap))
>  			return 0;
>  
> -		if (pcie_cap == 0xffffffff)
> -			return 0;
> +		if (PCI_EXT_CAP_ID(pcie_cap) == 0x0000 ||
> +			PCI_EXT_CAP_ID(pcie_cap) == 0xffff)
> +			break;
>  
>  		if (PCI_EXT_CAP_ID(pcie_cap) == PCI_EXT_CAP_ID_VNDR) {
>  			raw_pci_ext_ops->read(pci_domain_nr(bus), bus->number,
> @@ -76,7 +77,7 @@ static int fixed_bar_cap(struct pci_bus *bus, unsigned int devfn)
>  				return pos;
>  		}
>  
> -		pos = pcie_cap >> 20;
> +		pos = PCI_EXT_CAP_NEXT(pcie_cap);
>  	}
>  
>  	return 0;

Looks good.

Reviewed-by: Jesse Barnes <jbarnes@...tuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center
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