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    x86/cpufeature: Replace the old static_cpu_has() with safe variant · bc696ca0
    Borislav Petkov 提交于
    So the old one didn't work properly before alternatives had run.
    And it was supposed to provide an optimized JMP because the
    assumption was that the offset it is jumping to is within a
    signed byte and thus a two-byte JMP.
    
    So I did an x86_64 allyesconfig build and dumped all possible
    sites where static_cpu_has() was used. The optimization amounted
    to all in all 12(!) places where static_cpu_has() had generated
    a 2-byte JMP. Which has saved us a whopping 36 bytes!
    
    This clearly is not worth the trouble so we can remove it. The
    only place where the optimization might count - in __switch_to()
    - we will handle differently. But that's not subject of this
    patch.
    Signed-off-by: NBorislav Petkov <bp@suse.de>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/1453842730-28463-6-git-send-email-bp@alien8.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
    bc696ca0
cpufeature.h 8.4 KB