• David S. Miller's avatar
    sparc64: Make PAGE_OFFSET variable. · b2d43834
    David S. Miller authored
    Choose PAGE_OFFSET dynamically based upon cpu type.
    
    Original UltraSPARC-I (spitfire) chips only supported a 44-bit
    virtual address space.
    
    Newer chips (T4 and later) support 52-bit virtual addresses
    and up to 47-bits of physical memory space.
    
    Therefore we have to adjust PAGE_SIZE dynamically based upon
    the capabilities of the chip.
    
    Note that this change alone does not allow us to support > 43-bit
    physical memory, to do that we need to re-arrange our page table
    support.  The current encodings of the pmd_t and pgd_t pointers
    restricts us to "32 + 11" == 43 bits.
    
    This change can waste quite a bit of memory for the various tables.
    In particular, a future change should work to size and allocate
    kern_linear_bitmap[] and sparc64_valid_addr_bitmap[] dynamically.
    This isn't easy as we really cannot take a TLB miss when accessing
    kern_linear_bitmap[].  We'd have to lock it into the TLB or similar.
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    Acked-by: default avatarBob Picco <bob.picco@oracle.com>
    b2d43834
vmlinux.lds.S 2.87 KB