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From: Zhenzhong Duan <zhenzhong.duan@oracle.com>
To: JBeulich@suse.com, andrew.cooper3@citrix.com
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Xen-Devel <xen-devel@lists.xen.org>,
	Srinivas REDDY Eeda <srinivas.eeda@oracle.com>
Subject: [PATCH] Choose retpoline only when it is safe to use
Date: Tue, 6 Feb 2018 00:43:02 -0800 (PST)	[thread overview]
Message-ID: <d4c3bc09-c284-4372-acb4-27f0d913afe2@default> (raw)

When ( ibrs && thunk == THUNK_DEFAULT && !retpoline_safe() ) is true,
thunk is set to THUNK_JMP rather than THUNK_RETPOLINE.

When (!ibrs && thunk == THUNK_DEFAULT && !retpoline_safe() ) is true,
we should do the same.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
---
 xen/arch/x86/spec_ctrl.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index f10ffbf..ab4b244 100644
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -247,10 +247,10 @@ void __init init_speculation_mitigations(void)
 
     /*
      * If there are still no thunk preferences, the compiled default is
-     * actually retpoline, and it is better than nothing.
+     * actually retpoline, and it is better than nothing if it's retpoline safe.
      */
     if ( thunk == THUNK_DEFAULT )
-        thunk = THUNK_RETPOLINE;
+        thunk = retpoline_safe() ? THUNK_RETPOLINE : THUNK_JMP;
 
     /* Apply the chosen settings. */
     if ( thunk == THUNK_LFENCE )
-- 
1.7.3

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             reply	other threads:[~2018-02-06  8:43 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-06  8:43 Zhenzhong Duan [this message]
2018-02-06  8:59 ` [PATCH] Choose retpoline only when it is safe to use Andrew Cooper
2018-02-06  9:13   ` Zhenzhong Duan
2018-02-06  9:20     ` Andrew Cooper

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