linux-kernel - Re: [PATCH] x86/pci: intel ioh need to subtract mmconf range

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Date:	Thu, 14 Jan 2010 15:38:08 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
CC:	Jeff Garrett <jeff@...rrett.org>, linux-kernel@...r.kernel.org,
	Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-pci@...r.kernel.org, David Airlie <airlied@...ux.ie>
Subject: Re: [PATCH] x86/pci: intel ioh need to subtract mmconf range

On 01/14/2010 03:09 PM, Bjorn Helgaas wrote:
> On Thursday 14 January 2010 03:46:35 pm Yinghai Lu wrote:
>>
>> Bjorn pointed out we need to remove mmconf range
>>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>>
>> ---
>>  arch/x86/pci/intel_bus.c |   29 +++++++++++++++++++++++++++--
>>  1 file changed, 27 insertions(+), 2 deletions(-)
>>
>> Index: linux-2.6/arch/x86/pci/intel_bus.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/pci/intel_bus.c
>> +++ linux-2.6/arch/x86/pci/intel_bus.c
>> @@ -46,6 +46,20 @@ static inline void print_ioh_resources(s
>>  
>>  #define RANGE_NUM 16
>>  
>> +static void __devinit subtract_mmconf(struct range *range, int nr)
>> +{
>> +#ifdef CONFIG_PCI_MMCONFIG
>> +	struct pci_mmcfg_region *cfg;
>> +
>> +	if (list_empty(&pci_mmcfg_list))
>> +		return;
>> +
>> +        list_for_each_entry(cfg, &pci_mmcfg_list, list)
>> +		subtract_range(range, nr, cfg->res.start,
>> +			 cfg->res.end + 1);
>> +#endif
> 
> This can't be right, can it?  Let's say the kernel was built with
> CONFIG_PCI_MMCONFIG turned off, or the user used "pci=nommconf",
> or the kernel decides not to use MMCONFIG for some other reason.
> 
> In that case, the hardware may still be configured to support
> MMCONFIG, but the pci_mmcfg_list will be empty, so your code will
> leave the window alone.  We might assign some of that MMCONFIG
> space to a device, but the hardware will route it to MMCONFIG,
> not to the device.

so if there is mmconf specified, we just skip the whole function?

YH
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