From: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Date: Wed, 10 Oct 2018 09:07:18 +0000 (+0800)
Subject: x86/bugs/IBRS: properly use the _base ops if IBRS is currently unset
X-Git-Tag: v4.1.12-124.31.3~491
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8b44d2a3d7ada0818db085f453c4444adb21b82b;p=users%2Fjedix%2Flinux-maple.git

x86/bugs/IBRS: properly use the _base ops if IBRS is currently unset

... or else we can run into an idle state with IBRS enabled which lead to
low performance.

Orabug: 28782729

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
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 900fc409aea4..07eefe862036 100644
--- a/arch/x86/kernel/cpu/bugs_64.c
+++ b/arch/x86/kernel/cpu/bugs_64.c
@@ -266,7 +266,7 @@ void x86_spec_ctrl_set(u64 val)
 			else
 				host = val & ~(SPEC_CTRL_SSBD);
 		} else {
-			if (ibrs_inuse)
+			if (ibrs_inuse && (val & SPEC_CTRL_IBRS))
 				host = this_cpu_read(x86_spec_ctrl_priv_cpu);
 			else
 				host = x86_spec_ctrl_base;