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273b493689
We need PTE bits 3 ,4, 5, 6 and 57 to support protection-keys, because these are the bits we want to consolidate on across all configuration to support protection keys. Bit 3,4,5 and 6 are currently used on 4K-pte kernels. But bit 9 and 10 are available. Hence we use the two available bits and free up bit 5 and 6. We will still not be able to free up bit 3 and 4. In the absence of any other free bits, we will have to stay satisfied with what we have :-(. This means we will not be able to support 32 protection keys, but only 8. The bit numbers are big-endian as defined in the ISA3.0 This patch does the following change to 4K PTE. H_PAGE_F_SECOND (S) which occupied bit 4 moves to bit 7. H_PAGE_F_GIX (G,I,X) which occupied bit 5, 6 and 7 also moves to bit 8,9, 10 respectively. H_PAGE_HASHPTE (H) which occupied bit 8 moves to bit 4. Before the patch, the 4k PTE format was as follows 0 1 2 3 4 5 6 7 8 9 10....................57.....63 : : : : : : : : : : : : : v v v v v v v v v v v v v ,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-, |x|x|x|B|S |G |I |X |H| | |x|x|................| |x|x|x| '_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_' After the patch, the 4k PTE format is as follows 0 1 2 3 4 5 6 7 8 9 10....................57.....63 : : : : : : : : : : : : : v v v v v v v v v v v v v ,-,-,-,-,--,--,--,--,-,-,-,-,-,------------------,-,-,-, |x|x|x|B|H | | |S |G|I|X|x|x|................| |.|.|.| '_'_'_'_'__'__'__'__'_'_'_'_'_'________________'_'_'_'_' The patch has no code changes; just swizzles around bits. Signed-off-by: Ram Pai <linuxram@us.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
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