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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