From: Jiri Kosina <jkosina@suse.cz>
Subject: x86/bugs: do not default to IBRS even on SKL
Patch-mainline: never, SUSE specific
References: bsc#1068032 CVE-2017-5753 bsc#1112824 jsc#SLE-7074

Disable SUSE-specific IBRS-on-SKL implementation. Please refer to page 16 of

https://software.intel.com/security-software-guidance/api-app/sites/default/files/Retpoline-A-Branch-Target-Injection-Mitigation.pdf

Signed-off-by: Jiri Kosina <jkosina@suse.cz>

---
 arch/x86/kernel/cpu/bugs.c |   27 ---------------------------
 1 file changed, 27 deletions(-)

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -879,23 +879,6 @@ static enum spectre_v2_mitigation_cmd __
 	return cmd;
 }
 
-/* Check for Skylake-like CPUs (for RSB and IBRS handling) */
-static bool __init is_skylake_era(void)
-{
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
-	    boot_cpu_data.x86 == 6) {
-		switch (boot_cpu_data.x86_model) {
-		case INTEL_FAM6_SKYLAKE_MOBILE:
-		case INTEL_FAM6_SKYLAKE_DESKTOP:
-		case INTEL_FAM6_SKYLAKE_X:
-		case INTEL_FAM6_KABYLAKE_MOBILE:
-		case INTEL_FAM6_KABYLAKE_DESKTOP:
-			return true;
-		}
-	}
-	return false;
-}
-
 /* Disable in-kernel use of non-RSB RET predictors */
 static void __init spec_ctrl_disable_kernel_rrsba(void)
 {
@@ -955,16 +938,6 @@ static void __init spectre_v2_select_mit
 			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 			goto specv2_set_mode;
 		}
-
-		/*
-		 * If we have IBRS support, and either Skylake or !RETPOLINE,
-		 * then that's what we do.
-		 */
-		if (boot_cpu_has(X86_FEATURE_IBRS) && is_skylake_era()) {
-			mode = SPECTRE_V2_IBRS;
-			setup_force_cpu_cap(X86_FEATURE_USE_IBRS);
-			goto specv2_set_mode;
-		}
 		/* fall through */
 	case SPECTRE_V2_CMD_RETPOLINE:
 		if (IS_ENABLED(CONFIG_RETPOLINE))