Re: clean way to support >32bit addr on 32bit CPU

[Randy.Dunlap]

William Lee Irwin III wrote:
> On Mon, Jan 10, 2005 at 05:30:25PM -0800, Linus Torvalds wrote:
>
> > I don't think ioaddr_t needs to match resources. None of the IO accessor
> > functions take "u64"s anyway - and aren't likely to do so in the future
> > either - so "unsigned long" should be good enough.
> > Having u64 for resource handling is mainly an issue for RAM and
> > memory-mapped IO (right now the 32-bit limit means that we throw away
> > information about stuff above the 4GB mark from the e820 interfaces on
> > x86, for example - that _happens_ to work because we never see anything 
> > but RAM there anyway, but it means that /proc/iomem doesn't show all of 
> > the system RAM, and it does mean that our resource management doesn't 
> > actually handle 64-bit addresses correctly. 
> > See drivers/pci/probe.c for the result:
> > 	"PCI: Unable to handle 64-bit address for device xxxx"
> > (and I do not actually think this has _ever_ happened in real life, which 
> > makes me suspect that Windows doesn't handle them either - but it 
> > inevitably will happen some day).
>
>
> I have a vague recollection of seeing a report of an ia32 device and/or
> machine with this property from John Fusco but am having a tough time
> searching the archives properly for it. I do recall it being around the
> time the remap_pfn_range() work was started, and I also claimed it as
> one of the motivators of it in one of my posts. I'm unaware of whether
> there are more general resources in John Fusco's situation.
>
> My follow-ups began with:
> Message-ID: <20040924021735.GL9106@xxxxxxxxxxxxxx>
> References: <41535AAE.6090700@xxxxxxxxx>

http://marc.theaimsgroup.com/?l=linux-mm&m=109598180125156&w=2

--
~Randy
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