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

On Tue, Jan 19, 2021, Borislav Petkov wrote:

On Mon, Jan 18, 2021 at 04:26:49PM +1300, Kai Huang wrote:

quoted

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.