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    SubjectRe: [PATCH] x86/cpufeatures: Cleanup AMD speculation feature bits
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    On 1/26/2018 4:10 PM, Borislav Petkov wrote:
    > On Fri, Jan 26, 2018 at 09:59:44PM +0000, David Woodhouse wrote:
    >> If we wanted to do this kind of thing, we'd do it the other way round.
    >> Turn the *Intel* feature into both 'IBRS' and 'IBPB' CPU-visible
    >> features, and have those defined in the AMD word.
    >
    > You lost me here: have those defined in the AMD word?
    >
    >> Then use virtual bits with "" for the software features, since we
    >> don't want *those* to appear in /proc/cpuinfo.
    >
    > Whatever we do, I think it would be most consistent to have three
    > strings, *both* on Intel and AMD visible in cpuinfo: "ibrs", "ibpb" and
    > "stibp" so that there's no confusion what is enabled on each box.
    >
    > Now, those three can be the *virtual* features which get set by the
    > actual CPUID features on init. And the latter, the *actual* CPUID
    > features don't need to be visible in cpuinfo: people shouldn't care
    > whether "spec_ctrl" on Intel and "pred_cmd" on AMD both mean "ibpb". It
    > should be simply "ibpb" on both vendors in cpuinfo.
    >
    > Ditto for the others.
    >
    > This way you have one unified message of what is enabled on *any* box.

    That sounds good to me.

    Thanks,
    Tom

    >

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