powerpc: Update 64bit __copy_tofrom_user() using CPU_FTR_UNALIGNED_LD_STD
PATCH 1/1 powerpc: Update 64bit __copy_tofrom_user() using CPU_FTR_UNALIGNED_LD_STD
In exactly the same way that we updated memcpy() with new feature sections in commit 25d6e2d7c58ddc4a3b614fc5381591c0cfe66556 we do the same thing here for __copy_tofrom_user(). Once again this is purely a performance tweak for Cell and Power6 - this has no effect on all the other 64bit powerpc chips.
We can make these same changes to __copy_tofrom_user() because the basic copy algorithm is the same as in memcpy() - this version just has all the exception handling logic needed when copying to or from userspace as well as a special case for copying whole 4K pages that are page aligned.
CPU_FTR_UNALIGNED_LD_STD CPU was added in commit4ec577a28980a0790df3c3dfe9c81f6e2222acfb
We also make the same simple one line change from cmpldi r1,... to cmpldi cr1,... for consistency.
--- arch/powerpc/lib/copyuser_64.S | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
arch/powerpc/lib/copyuser_64.S +15 -2
@@ -26,11 +26,24 @@ _GLOBAL(__copy_tofrom_user) andi. r6,r6,7 PPC_MTOCRF 0x01,r5 blt cr1,.Lshort_copy +/* Below we want to nop out the bne if we're on a CPU that has the + * CPU_FTR_UNALIGNED_LD_STD bit set and the CPU_FTR_CP_USE_DCBTZ bit + * cleared. + * At the time of writing the only CPU that has this combination of bits + * set is Power6. + */ +BEGIN_FTR_SECTION + nop +FTR_SECTION_ELSE bne .Ldst_unaligned +ALT_FTR_SECTION_END(CPU_FTR_UNALIGNED_LD_STD | CPU_FTR_CP_USE_DCBTZ, \ + CPU_FTR_UNALIGNED_LD_STD) .Ldst_aligned: - andi. r0,r4,7 addi r3,r3,-16 +BEGIN_FTR_SECTION + andi. r0,r4,7 bne .Lsrc_unaligned +END_FTR_SECTION_IFCLR(CPU_FTR_UNALIGNED_LD_STD) srdi r7,r5,4 20: ld r9,0(r4) addi r4,r4,-8
@@ -138,7 +151,7 @@ _GLOBAL(__copy_tofrom_user) PPC_MTOCRF 0x01,r6 /* put #bytes to 8B bdry into cr7 */ subf r5,r6,r5 li r7,0 - cmpldi r1,r5,16 + cmpldi cr1,r5,16 bf cr7*4+3,1f 35: lbz r0,0(r4) 81: stb r0,0(r3)