Re: RFC: 64-bit resources and changes to pci, ioremap, ...

[Doug Reiland]

current pentium4 have this problem as well. Shouldn't
need to use the emt64 (x86_64) mode. It takes i/o
bridges and MCH to support it, but the latest Intel
ones do. However, I am pretty sure BIOSes wouldn't
assign the pci/pci-e addresses > 4GIG so most are not
impacted.


--- Kumar Gala <kumar.gala@xxxxxxxxxxxxx> wrote:

> As I started to update the existing patches to make
> struct resource  
> have 64-bit start and end values I started to see
> all the places that  
> this effects and was hoping to get some discussion
> on what direction  
> we want to take.
> 
> One of the main reasons to make this change is to
> handle processors  
> that have larger physical address space than
> effective.  A number of  
> higher-end embedded processors are starting to
> support larger  
> physical address space while still having a 32-bit
> effective  
> address.  I was wondering if any x86 variants
> support this type of  
> feature?
> 
> The main issue that I'm starting to see is that the
> concept of a  
> physical address from the processors point of view
> needs to be  
> consistent throughout all subsystems of the kernel. 
> Currently the  
> major usage of struct resource is with the PCI
> subsystem and PCI  
> drivers.  The following are some questions that I
> was hoping to get  
> answers to and discussion around:
> 
> * How many 32-bit systems support larger than 32-bit
> physical  
> addresses (I know newer PPCs do)?
> * How many 32-bit systems support a 64-bit PCI
> address space?
> * Should ioremap and variants start taking 64-bit
> physical addresses?
> * Do we make this an arch option and wrap start and
> end in a typedef  
> similar to pte_t and provide accessor macros to
> ensure proper use?
> 
> Andrew has also asked me to post size comparisons of
> drivers/*/*.o  
> building allmodconfig with 32-bit resources and
> 64-bit resources to  
> see what the size growth is.  I'll post logs for
> people to take a  
> look at in a followup email.
> 
> - Kumar
> 



		
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