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    SubjectRe: [RFC][PATCH 02/17] x86/cpu: Clean up SRSO return thunk mess
    On Wed, Aug 09, 2023 at 09:12:20AM +0200, Peter Zijlstra wrote:
    > Where Zen1/2 flush the BTB using the instruction decoder trick
    > (test,movabs) Zen3/4 use instruction aliasing. SRSO adds RSB (RAP in

    BTB aliasing.

    > AMD speak) stuffing to force a return mis-predict.

    No it doesn't. It causes BTB aliasing which evicts any potentially
    poisoned entries.

    > That is; the AMD retbleed is a form of Speculative-Type-Confusion
    > where the branch predictor is trained to use the BTB to predict the
    > RET address, while AMD inception/SRSO is a form of
    > Speculative-Type-Confusion where another instruction is trained to be
    > treated like a CALL instruction and poison the RSB (RAP).

    Nope, Andy explained it already in the 0th message.

    > Pick one of three options at boot.

    Yes, provided microarchitecturally that works, I'm all for removing the
    __ret alternative.

    Thx.

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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