• Ram Pai's avatar
    powerpc: Free up four 64K PTE bits in 64K backed HPTE pages · bf9a95f9
    Ram Pai authored
    Rearrange 64K PTE bits to free up bits 3, 4, 5 and 6
    in the 64K backed HPTE pages. This along with the earlier
    patch will entirely free up the four bits from 64K PTE.
    The bit numbers are big-endian as defined in the ISA3.0
    
    This patch does the following change to 64K PTE backed
    by 64K HPTE.
    
    H_PAGE_F_SECOND (S) which occupied bit 4 moves to the
    	second part of the pte to bit 60.
    H_PAGE_F_GIX (G,I,X) which occupied bit 5, 6 and 7 also
    	moves to the second part of the pte to bit 61,
     	62, 63, 64 respectively
    
    since bit 7 is now freed up, we move H_PAGE_BUSY (B) from
    bit 9 to bit 7.
    
    The second part of the PTE will hold
    (H_PAGE_F_SECOND|H_PAGE_F_GIX) at bit 60,61,62,63.
    NOTE: None of the bits in the secondary PTE were not used
    by 64k-HPTE backed PTE.
    
    Before the patch, the 64K HPTE backed 64k PTE format was
    as follows
    
     0 1 2 3 4  5  6  7  8 9 10...........................63
     : : : : :  :  :  :  : : :                            :
     v v v v v  v  v  v  v v v                            v
    
    ,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-,
    |x|x|x| |S |G |I |X |x|B| |x|x|................|x|x|x|x| <- primary pte
    '_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_'
    | | | | |  |  |  |  | | | | |..................| | | | | <- secondary pte
    '_'_'_'_'__'__'__'__'_'_'_'_'__________________'_'_'_'_'
    
    After the patch, the 64k HPTE backed 64k PTE format is
    as follows
    
     0 1 2 3 4  5  6  7  8 9 10...........................63
     : : : : :  :  :  :  : : :                            :
     v v v v v  v  v  v  v v v                            v
    
    ,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-,
    |x|x|x| |  |  |  |B |x| | |x|x|................|.|.|.|.| <- primary pte
    '_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_'
    | | | | |  |  |  |  | | | | |..................|S|G|I|X| <- secondary pte
    '_'_'_'_'__'__'__'__'_'_'_'_'__________________'_'_'_'_'
    
    The above PTE changes is applicable to hugetlbpages aswell.
    
    The patch does the following code changes:
    
    a) moves the H_PAGE_F_SECOND and H_PAGE_F_GIX to 4k PTE
    	header since it is no more needed b the 64k PTEs.
    b) abstracts out __real_pte() and __rpte_to_hidx() so the
    	caller need not know the bit location of the slot.
    c) moves the slot bits to the secondary pte.
    Reviewed-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    Signed-off-by: default avatarRam Pai <linuxram@us.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    bf9a95f9
hash.h 6.06 KB