Re: 2.6.27-rc1 >4096MB issue

[Jeremy Fitzhardinge <jeremy@goop.org>]

Jan Beulich wrote:
>>>> Jeremy Fitzhardinge <jeremy@goop.org> 05.08.08 05:07 >>>
>>>>         
>> Subject: make PFN_PHYS explicitly return 64-bit result
>>
>> PFN_PHYS, as its name suggests, turns a pfn into a physical address.
>> However, it is a macro which just operates on its argument without
>> modifying its type.  pfns are typed unsigned long, but an unsigned
>> long may not be long enough to hold a physical address (32-bit systems
>> with more than 32 bits of physcial address).  This means that the
>> resulting address could be truncated if it doesn't fit within an
>> unsigned long.  This isn't generally a problem because most users end
>> up using it for "low" memory, but there's no reason why PFN_PHYS
>> couldn't be used for any possible pfn.
>>
>> Unfortunately there's no univerally recognized type for holding a full
>> physical address, so this patch makes it always return a u64 result.
>>     
>
> Couldn't you use resource_size_t here?

Yeah, looks like I can.  It had crossed my mind, but I'd vaguely 
remembered that it might no be set if you don't have 64-bit IO devices.  
But it looks like it's set for all interesting cases (64 bit machines, 
and 32-bit x86 PAE).

    J