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This switch few of the page table accessor to use the __raw variant
and does the cpu to big endian conversion of constants. This helps in
generating better code.
For ex: a pgd_none(pgd) check with and without fix is listed below
Without fix:
------------
2240: 20 00 61 eb ld r27,32(r1)
/* PGD level */
typedef struct { __be64 pgd; } pgd_t;
static inline unsigned long pgd_val(pgd_t x)
{
return be64_to_cpu(x.pgd);
2244: 22 00 66 78 rldicl r6,r3,32,32
2248: 3e 40 7d 54 rotlwi r29,r3,8
224c: 0e c0 7d 50 rlwimi r29,r3,24,0,7
2250: 3e 40 c5 54 rotlwi r5,r6,8
2254: 2e c4 7d 50 rlwimi r29,r3,24,16,23
2258: 0e c0 c5 50 rlwimi r5,r6,24,0,7
225c: 2e c4 c5 50 rlwimi r5,r6,24,16,23
2260: c6 07 bd 7b rldicr r29,r29,32,31
2264: 78 2b bd 7f or r29,r29,r5
if (pgd_none(pgd))
2268: 00 00 bd 2f cmpdi cr7,r29,0
226c: 54 03 9e 41 beq cr7,25c0 <__get_user_pages_fast+0x500>
With fix:
---------
2370: 20 00 61 eb ld r27,32(r1)
if (pgd_none(pgd))
2374: 00 00 bd 2f cmpdi cr7,r29,0
2378: a8 03 9e 41 beq cr7,2720 <__get_user_pages_fast+0x530>
break;
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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Traditionally Power server machines have used the Hashed Page Table MMU
mode. In this mode Linux manages its own tree of nested page tables,
aka. "the Linux page tables", which are not used by the hardware
directly, and software loads translations into the hash page table for
use by the hardware.
Power ISA 3.0 defines a new MMU mode, known as Radix Tree Translation,
where the hardware can directly operate on the Linux page tables.
However the hardware requires that the page tables be in big endian
format.
To accommodate this, switch the pgtable types to __be64 and add
appropriate endian conversions.
Because we will be supporting a single kernel binary that boots using
either radix or hash mode, we always store the Linux page tables big
endian, even in hash mode where they are not actually used by the
hardware.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Fix sparse errors, flesh out change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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