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Borislav Petkov authored
... instead of the semi-version with the spelled out sections. What is more, make the REP_GOOD version be the default copy_page() version as the majority of the relevant x86 CPUs do set X86_FEATURE_REP_GOOD. Thus, copy_page gets compiled to: ffffffff8130af80 <copy_page>: ffffffff8130af80: e9 0b 00 00 00 jmpq ffffffff8130af90 <copy_page_regs> ffffffff8130af85: b9 00 02 00 00 mov $0x200,%ecx ffffffff8130af8a: f3 48 a5 rep movsq %ds:(%rsi),%es:(%rdi) ffffffff8130af8d: c3 retq ffffffff8130af8e: 66 90 xchg %ax,%ax ffffffff8130af90 <copy_page_regs>: ... and after the alternatives have run, the JMP to the old, unrolled version gets NOPed out: ffffffff8130af80 <copy_page>: ffffffff8130af80: 66 66 90 xchg %ax,%ax ffffffff8130af83: 66 90 xchg %ax,%ax ffffffff8130af85: b9 00 02 00 00 mov $0x200,%ecx ffffffff8130af8a: f3 48 a5 rep movsq %ds:(%rsi),%es:(%rdi) ffffffff8130af8d: c3 retq On modern uarches, those NOPs are cheaper than the unconditional JMP previously. Signed-off-by:
Borislav Petkov <bp@suse.de>
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