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

On 8/9/2021 9:06 AM, Borislav Petkov wrote:

On Thu, Jul 22, 2021 at 01:51:51PM -0700, Yu-cheng Yu wrote:

quoted

  /*
   * 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).