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    SubjectRe: [PATCH v4 12/12] x86/traps: Fix up invalid PASID
    On Fri, Jun 26, 2020 at 11:44:50AM +0200, Peter Zijlstra wrote:
    > On Thu, Jun 25, 2020 at 01:17:22PM -0700, Fenghua Yu wrote:
    >
    > > +static bool fixup_pasid_exception(void)
    > > +{
    > > + if (!IS_ENABLED(CONFIG_INTEL_IOMMU_SVM))
    > > + return false;
    > > + if (!static_cpu_has(X86_FEATURE_ENQCMD))
    > > + return false;
    >
    > elsewhere you had another variation:
    >
    > + if (!IS_ENABLED(CONFIG_INTEL_IOMMU_SVM))
    > + return;
    > +
    > + if (!cpu_feature_enabled(X86_FEATURE_ENQCMD))
    > + return;
    >
    > Which is it, and why do we need the CONFIG thing when combined with the
    > enabled thing?

    Do we have a standard way of coding for a feature that depends on multiple
    other features? For this case the system needs to both suport the ENQCMD
    instruction, and also have kernel code that programs the IOMMU.

    And/or guidance on when to use each of the very somewhat simlar looking
    boot_cpu_has()
    static_cpu_has()
    IS_ENABLED()
    cpu_feature_enabled()
    options?

    -Tony

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