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Old 02-27-2009, 07:21 AM   #1
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Registered: Jul 2008
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physical memory allocation over 4b

Hello folks,

I have a 64 bit dma that I have to program with 64 bit physical
beyond 4 gb because I have to test dma with memory allocation beyond
4 gb.
I 'm using linux x86_64 2.6.24 and I have 8 gb ram.
How can I allocate physical dma memory beyond 4gb ? In x86_64
can I use __pa to have physical address ?

I would like to find a function that returns a physical adddres beyond
and then i write phys address in dma register .

Old 02-28-2009, 01:03 AM   #2
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you know you should let people know if you are using a vanilla kernel or some distro that dose not use a vanila kernel. It is the gernel that runs the cpu so it will see and use over 4 gbas far as slackware just use the huge smp. kernel.


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