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    SubjectRe: [PATCH v9 10/14] x86/cpu/keylocker: Check Gather Data Sampling mitigation
    On Thu, Mar 28, 2024 at 06:53:42PM -0700, Chang S. Bae wrote:
    > +/*
    > + * The mitigation is implemented at a microcode level. Ensure that the
    > + * microcode update is applied and the mitigation is locked.
    > + */
    > +static bool __init have_gds_mitigation(void)
    > +{
    > + u64 mcu_ctrl;
    > +
    > + /* GDS_CTRL is set if new microcode is loaded. */
    > + if (!(x86_read_arch_cap_msr() & ARCH_CAP_GDS_CTRL))
    > + goto vulnerable;
    > +
    > + /* If GDS_MITG_LOCKED is set, GDS_MITG_DIS is forced to 0. */
    > + rdmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl);
    > + if (mcu_ctrl & GDS_MITG_LOCKED)
    > + return true;

    Similar to RFDS, above checks can be simplified to:

    if (gds_mitigation == GDS_MITIGATION_FULL_LOCKED)
    return true;
    > +
    > +vulnerable:
    > + pr_warn("x86/keylocker: Susceptible to the GDS vulnerability.\n");
    > + return false;
    > +}

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