• Maciej W. Rozycki's avatar
    x86: APIC: remove apic_write_around(); use alternatives · 593f4a78
    Maciej W. Rozycki authored
    Use alternatives to select the workaround for the 11AP Pentium erratum
    for the affected steppings on the fly rather than build time.  Remove the
    X86_GOOD_APIC configuration option and replace all the calls to
    apic_write_around() with plain apic_write(), protecting accesses to the
    ESR as appropriate due to the 3AP Pentium erratum.  Remove
    apic_read_around() and all its invocations altogether as not needed.
    Remove apic_write_atomic() and all its implementing backends.  The use of
    ASM_OUTPUT2() is not strictly needed for input constraints, but I have
    used it for readability's sake.
    
    I had the feeling no one else was brave enough to do it, so I went ahead
    and here it is.  Verified by checking the generated assembly and tested
    with both a 32-bit and a 64-bit configuration, also with the 11AP
    "feature" forced on and verified with gdb on /proc/kcore to work as
    expected (as an 11AP machines are quite hard to get hands on these days).
    Some script complained about the use of "volatile", but apic_write() needs
    it for the same reason and is effectively a replacement for writel(), so I
    have disregarded it.
    
    I am not sure what the policy wrt defconfig files is, they are generated
    and there is risk of a conflict resulting from an unrelated change, so I
    have left changes to them out.  The option will get removed from them at
    the next run.
    
    Some testing with machines other than mine will be needed to avoid some
    stupid mistake, but despite its volume, the change is not really that
    intrusive, so I am fairly confident that because it works for me, it will
    everywhere.
    Signed-off-by: default avatarMaciej W. Rozycki <macro@linux-mips.org>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    593f4a78
mach_apic.h 4.46 KB