• Vasily Gorbik's avatar
    s390: introduce CPU alternatives · 686140a1
    Vasily Gorbik authored
    Implement CPU alternatives, which allows to optionally patch newer
    instructions at runtime, based on CPU facilities availability.
    A new kernel boot parameter "noaltinstr" disables patching.
    Current implementation is derived from x86 alternatives. Although
    ideal instructions padding (when altinstr is longer then oldinstr)
    is added at compile time, and no oldinstr nops optimization has to be
    done at runtime. Also couple of compile time sanity checks are done:
    1. oldinstr and altinstr must be <= 254 bytes long,
    2. oldinstr and altinstr must not have an odd length.
    alternative(oldinstr, altinstr, facility);
    alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2);
    Both compile time and runtime padding consists of either 6/4/2 bytes nop
    or a jump (brcl) + 2 bytes nop filler if padding is longer then 6 bytes.
    .altinstructions and .altinstr_replacement sections are part of
    __init_begin : __init_end region and are freed after initialization.
    Signed-off-by: default avatarVasily Gorbik <gor@linux.vnet.ibm.com>
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
kernel-parameters.txt 160 KB