From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Fri, 29 Dec 2017 19:45:40 +0000 (-0500)
Subject: x86/spec_ctrl: Disable if running as Xen PV guest.
X-Git-Tag: v4.1.12-124.31.3~1389
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=93a55b77518d862edfb61ce016ed110b9356d5ff;p=users%2Fjedix%2Flinux-maple.git

x86/spec_ctrl: Disable if running as Xen PV guest.


Orabug: 27344012
CVE: CVE-2017-5715

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>
---

diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index 61216c821682..1dd9a5b09e01 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -86,8 +86,15 @@ void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 	}
 
 	if (!c->cpu_index) {
+		bool ignore = false;
+
+		if (xen_pv_domain())
+			ignore = true;
+
 		if (boot_cpu_has(X86_FEATURE_SPEC_CTRL)) {
-			printk(KERN_INFO "FEATURE SPEC_CTRL Present\n");
+			printk(KERN_INFO "FEATURE SPEC_CTRL Present%s\n", ignore ? " but ignored (Xen)": "");
+			if (ignore)
+				return;
 			set_ibrs_supported();
 			set_ibpb_supported();
 			if (ibrs_inuse)
@@ -95,7 +102,9 @@ void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 			if (ibpb_inuse)
 				sysctl_ibpb_enabled = 1;
 		} else if (boot_cpu_has(X86_FEATURE_IBPB)) {
-			printk_once(KERN_INFO "FEATURE IBPB Present\n");
+			printk_once(KERN_INFO "FEATURE IBPB Present%s\n", ignore ? " but ignored (Xen)": "");
+			if (ignore)
+				return;
 			set_ibpb_supported();
 			if (ibpb_inuse)
 				sysctl_ibpb_enabled = 1;