From: William Roche <william.roche@oracle.com>
Date: Sat, 16 Feb 2019 01:06:17 +0000 (-0500)
Subject: x86/speculation: Dynamic enable and disable of RSB stuffing with IBRS&!SMEP
X-Git-Tag: v4.1.12-124.31.3~89
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=01526ef58652f1dc731c619e7c58e9fc3854edf2;p=users%2Fjedix%2Flinux-maple.git

x86/speculation: Dynamic enable and disable of RSB stuffing with IBRS&!SMEP

As IBRS is a dynamic feature, RSB overwrite needs to also be dynamically
activated and disabled with IBRS (if SMEP is not available).

Signed-off-by: William Roche <william.roche@oracle.com>
Co-developed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>

(cherry picked from commit fe61cd8181780903b2e092e2079ee09a6eb733d9)

Orabug: 29660924

Signed-off-by: William Roche <william.roche@oracle.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Acked-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

Conflicts:
	arch/x86/kernel/cpu/bugs.c
	arch/x86/kernel/cpu/spec_ctrl.c
bugs.c vs bugs_64.c in UEK4
spec_ctrl.c code still in bugs_64.c on UEK4

Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/arch/x86/kernel/cpu/bugs_64.c b/arch/x86/kernel/cpu/bugs_64.c
index 5c27c37ee36b..688b3a8f2d59 100644
--- a/arch/x86/kernel/cpu/bugs_64.c
+++ b/arch/x86/kernel/cpu/bugs_64.c
@@ -573,9 +573,14 @@ void change_spectre_v2_mitigation(enum spectre_v2_mitigation_action action)
 			if (eibrs_supported)
 				spec_ctrl_flush_all_cpus(MSR_IA32_SPEC_CTRL,
 					x86_spec_ctrl_priv);
+			if (!boot_cpu_has(X86_FEATURE_SMEP)) {
+				/* IBRS without SMEP needs RSB overwrite */
+				rsb_overwrite_enable();
+			}
 		} else {
 			set_ibrs_disabled();
 			if (use_ibrs & SPEC_CTRL_IBRS_SUPPORTED) {
+				rsb_overwrite_disable();
 				spec_ctrl_flush_all_cpus(MSR_IA32_SPEC_CTRL,
 							 x86_spec_ctrl_base);
 			}
@@ -735,10 +740,13 @@ static void __init select_ibrs_variant(enum spectre_v2_mitigation *mode)
 static void disable_ibrs_and_friends(bool disable_ibpb)
 {
 	set_ibrs_disabled();
-	if (use_ibrs & SPEC_CTRL_IBRS_SUPPORTED)
-		/* Disable IBRS an all cpus */
+	if (use_ibrs & SPEC_CTRL_IBRS_SUPPORTED) {
+		rsb_overwrite_disable();
+		/* Disable IBRS on all cpus */
 		spec_ctrl_flush_all_cpus(MSR_IA32_SPEC_CTRL,
 			x86_spec_ctrl_base & ~SPEC_CTRL_FEATURE_ENABLE_IBRS);
+	}
+
 	/*
 	 * We need to use IBPB with retpoline if it is available.
 	 * Also IBRS for firmware paths.