Re: [PATCH v28 04/32] x86/cpufeatures: Introduce CPU setup and option parsing for CET

[Yu, Yu-cheng]

On 8/9/2021 9:06 AM, Borislav Petkov wrote:
> On Thu, Jul 22, 2021 at 01:51:51PM -0700, Yu-cheng Yu wrote:
> >   /*
> >    * Some CPU features depend on higher CPUID levels, which may not always
> >    * be available due to CPUID level capping or broken virtualization
> > @@ -1249,6 +1257,11 @@ static void __init cpu_parse_early_param(void)
> >   	if (cmdline_find_option_bool(boot_command_line, "noxsaves"))
> >   		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
> >   
> > +	if (cmdline_find_option_bool(boot_command_line, "no_user_shstk"))
> > +		setup_clear_cpu_cap(X86_FEATURE_SHSTK);
> > +	if (cmdline_find_option_bool(boot_command_line, "no_user_ibt"))
> > +		setup_clear_cpu_cap(X86_FEATURE_IBT);
>
> Patch 1 says:
>
> "Disabling shadow stack also disables IBT."
>
> I don't see that here.

We have X86_FEATURE_IBT dependent on X86_FEATURE_SHSTK (patch #3).