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

Yu, Yu-cheng
2021-08-10T15:40:06Z

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).