Re: [RFC PATCH v2 01/26] x86/cpufeatures: Add SGX1 and SGX2 sub-features

Sean Christopherson
2021-01-19T18:50:07Z

On Tue, Jan 19, 2021, Borislav Petkov wrote:
> On Mon, Jan 18, 2021 at 04:26:49PM +1300, Kai Huang wrote:
> > diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
> > index 3b1b01f2b248..7937a315f8cf 100644
> > --- a/arch/x86/kernel/cpu/feat_ctl.c
> > +++ b/arch/x86/kernel/cpu/feat_ctl.c
> > @@ -96,7 +96,6 @@ static void init_vmx_capabilities(struct cpuinfo_x86 *c)
> > static void clear_sgx_caps(void)
> > {
> > setup_clear_cpu_cap(X86_FEATURE_SGX);
> > - setup_clear_cpu_cap(X86_FEATURE_SGX_LC);
>
> Why is that line being removed here?
>
> Shouldn't this add SGX1 and SGX2 here instead as this function is
> supposed to, well, *clear* sgx caps on feat_ctl setup failures or
> "nosgx" cmdline?

Doesn't adding making the SGX sub-features depend on X86_FEATURE_SGX have the
same net effect? Or am I misreading do_clear_cpu_cap()?

Though if we use the cpuid_deps table, I'd vote to get rid of clear_sgx_caps()
and call setup_clear_cpu_cap(X86_FEATURE_SGX) directly. And probably change the
existing SGX_LC behavior and drop clear_sgx_caps() in a separate patch instead
of squeezing it into this one.