linux-kernel - [PATCH v2 7/8] x86: Do not use dynamic IBRS if retpoline is enabled

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Date:   Fri,  5 Jan 2018 18:12:22 -0800
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 7/8] x86: Do not use dynamic IBRS if retpoline is enabled

Don't use dynamic IBRS that toggle IBRS on entry/exit
to kernel code if retpoline is used.

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
---
 arch/x86/kernel/cpu/spec_ctrl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/cpu/spec_ctrl.c b/arch/x86/kernel/cpu/spec_ctrl.c
index 28107a2..076c470 100644
--- a/arch/x86/kernel/cpu/spec_ctrl.c
+++ b/arch/x86/kernel/cpu/spec_ctrl.c
@@ -26,10 +26,12 @@ DEFINE_MUTEX(spec_ctrl_mutex);
 
 static inline void set_ibrs_feature(void)
 {
+#if !defined(RETPOLINE)
 	if (!ibrs_admin_disabled) {
 		dynamic_ibrs = 1;
 		ibrs_enabled = IBRS_ENABLED;
 	}
+#endif
 }
 
 void scan_spec_ctrl_feature(struct cpuinfo_x86 *c)
-- 
2.9.4