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    SubjectRe: [patch RFC 5/5] x86/speculation: Add basic speculation control code
    On Wed, Jan 10, 2018 at 02:10:10PM +0100, Andrea Arcangeli wrote:
    > It's still incredibly faster to shutdown part of the CPU temporarily
    > than to flush its internal state as a whole with IBPB. If it wouldn't
    > be the case ibrs_enabled 0 ibpb_enabled 2 special mode would perform
    > better (but that's only enabled by default if SPEC_CTRL is not
    > available and only IBPB_SUPPORT is).

    Yet another bit of perhaps useful info: if you run 100% kernel
    intensive computation (i.e. only interrupts on idle task or a kernel
    driver doing all in kernel) ibrs_enabled 0 ibpb_enabled 2 of course is
    much faster than ibrs_enabled 1 ibpb_enabled 1. As long as you don't
    have frequent ring change, ibrs_enabled 0 ibpb_enabled 2 is faster.

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