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SubjectRe: [PATCH v15 05/23] x86/cpu/intel: Detect SGX support and update caps appropriately
On Mon, Nov 05, 2018 at 04:09:33PM +0200, Jarkko Sakkinen wrote:
> On Sat, Nov 03, 2018 at 03:05:39PM +0200, Andy Shevchenko wrote:
> > > +static void detect_sgx(struct cpuinfo_x86 *c)
> > > +{
> > > + bool unsupported = false;
> > > + unsigned long long fc;
> > > +
> > > + rdmsrl(MSR_IA32_FEATURE_CONTROL, fc);
> > > + if (!(fc & FEATURE_CONTROL_LOCKED)) {
> > > + pr_err_once("sgx: IA32_FEATURE_CONTROL MSR is not locked\n");
> > > + unsupported = true;
> > > + } else if (!(fc & FEATURE_CONTROL_SGX_ENABLE)) {
> > > + pr_err_once("sgx: not enabled in IA32_FEATURE_CONTROL MSR\n");
> > > + unsupported = true;
> > > + } else if (!cpu_has(c, X86_FEATURE_SGX1)) {
> > > + pr_err_once("sgx: SGX1 instruction set not supported\n");
> > > + unsupported = true;
> > > + }
> >
> > If you do
> >
> > } else {
> > /* Supported */
> > return;
> > }
>
> Agree. Would this be a more clean flow in the attached patch?

Actually I'll paste the whole function for clarity because it is not too
long:

static void detect_sgx(struct cpuinfo_x86 *c)
{
unsigned long long fc;

rdmsrl(MSR_IA32_FEATURE_CONTROL, fc);
if (!(fc & FEATURE_CONTROL_LOCKED)) {
pr_err_once("sgx: IA32_FEATURE_CONTROL MSR is not locked\n");
goto out_unsupported;
}

if (!(fc & FEATURE_CONTROL_SGX_ENABLE)) {
pr_err_once("sgx: not enabled in IA32_FEATURE_CONTROL MSR\n");
goto out_unsupported;
}

if (!cpu_has(c, X86_FEATURE_SGX1)) {
pr_err_once("sgx: SGX1 instruction set not supported\n");
goto out_unsupported;
}

if (!(fc & FEATURE_CONTROL_SGX_LE_WR)) {
pr_info_once("sgx: launch control MSRs are not writable\n");
goto out_msrs_rdonly;
}

return;
out_unsupported:
setup_clear_cpu_cap(X86_FEATURE_SGX);
setup_clear_cpu_cap(X86_FEATURE_SGX1);
setup_clear_cpu_cap(X86_FEATURE_SGX2);
out_msrs_rdonly:
setup_clear_cpu_cap(X86_FEATURE_SGX_LC);
}

/Jarkko

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