Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 15 Jun 2020 08:58:06 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Anthony Steinhauser <asteinhauser@google.com>
Cc:     linux-tip-commits@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>, x86 <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] x86/speculation: Merge one test in
 spectre_v2_user_select_mitigation()
Message-ID: <20200615065806.GB14668@zn.tnic>
References: <159169282952.17951.3529693809120577424.tip-bot2@tip-bot2>
 <20200611140951.GD30352@zn.tnic>
 <CAN_oZf16odNhpY6_LqkVY2wpy90jKM9-vgKo4LE8OJ-QTDCKiw@mail.gmail.com>
 <20200611154356.GE30352@zn.tnic>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20200611154356.GE30352@zn.tnic>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

(dropping stable@ from Cc).

---

Merge the test whether the CPU supports STIBP into the test which
determines whether STIBP is required. Thus try to simplify what is
already an insane logic.

Remove a superfluous newline in a comment, while at it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Anthony Steinhauser <asteinhauser@google.com>
---
 arch/x86/kernel/cpu/bugs.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0b71970d2d3d..7beaefa9d198 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -763,10 +763,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 	}
 
 	/*
-	 * If enhanced IBRS is enabled or SMT impossible, STIBP is not
+	 * If no STIBP, enhanced IBRS is enabled or SMT impossible, STIBP is not
 	 * required.
 	 */
-	if (!smt_possible || spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
+	if (!boot_cpu_has(X86_FEATURE_STIBP) ||
+	    !smt_possible ||
+	    spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
 		return;
 
 	/*
@@ -778,12 +780,6 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 	    boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
 		mode = SPECTRE_V2_USER_STRICT_PREFERRED;
 
-	/*
-	 * If STIBP is not available, clear the STIBP mode.
-	 */
-	if (!boot_cpu_has(X86_FEATURE_STIBP))
-		mode = SPECTRE_V2_USER_NONE;
-
 	spectre_v2_user_stibp = mode;
 
 set_mode:
@@ -1270,7 +1266,6 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
 		 * Indirect branch speculation is always disabled in strict
 		 * mode. It can neither be enabled if it was force-disabled
 		 * by a  previous prctl call.
-
 		 */
 		if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT ||
 		    spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||
-- 
2.21.0

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette