* MAX_PHYSADDR_BITS v/s MAX_PHYSMEM_BITS
@ 2011-12-20 13:34 chandan r
0 siblings, 0 replies; only message in thread
From: chandan r @ 2011-12-20 13:34 UTC (permalink / raw)
To: kernelnewbies
Hi all,
Consider the following code snippet (for x86_64 arch) from
arch/x86/include/asm/sparsemem.h:
# define SECTION_SIZE_BITS 27 /* matt - 128 is convenient right now */
# define MAX_PHYSADDR_BITS 44
# define MAX_PHYSMEM_BITS 46
Also, consider the following comments (obtained from the same file),
MAX_PHYSADDR_BITS 2^n: max size of physical address space
MAX_PHYSMEM_BITS 2^n: how much memory we can have in
that space
According to my understanding MAX_PHYSMEM_BITS has to have a value
less than or equal to MAX_PHYSADDR_BITS. But this is not the case
for x86_64. Can someone explain what these macros really mean?
Thanks,
chandan r
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2011-12-20 13:34 MAX_PHYSADDR_BITS v/s MAX_PHYSMEM_BITS chandan r
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