linux-kernel - [PATCH 4.9 03/24] x86/retpoline: Remove minimal retpoline support

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Message-Id: <20220309155856.398762008@linuxfoundation.org>
Date:   Wed,  9 Mar 2022 16:59:16 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Zhenzhong Duan <zhenzhong.duan@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Borislav Petkov <bp@...e.de>, "H. Peter Anvin" <hpa@...or.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        srinivas.eeda@...cle.com, Ben Hutchings <ben@...adent.org.uk>
Subject: [PATCH 4.9 03/24] x86/retpoline: Remove minimal retpoline support

From: Zhenzhong Duan <zhenzhong.duan@...cle.com>

commit ef014aae8f1cd2793e4e014bbb102bed53f852b7 upstream.

Now that CONFIG_RETPOLINE hard depends on compiler support, there is no
reason to keep the minimal retpoline support around which only provided
basic protection in the assembly files.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...cle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: David Woodhouse <dwmw@...zon.co.uk>
Cc: Borislav Petkov <bp@...e.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: <srinivas.eeda@...cle.com>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/f06f0a89-5587-45db-8ed2-0a9d6638d5c0@default
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/include/asm/nospec-branch.h |    2 --
 arch/x86/kernel/cpu/bugs.c           |   13 ++-----------
 2 files changed, 2 insertions(+), 13 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -223,8 +223,6 @@
 /* The Spectre V2 mitigation variants */
 enum spectre_v2_mitigation {
 	SPECTRE_V2_NONE,
-	SPECTRE_V2_RETPOLINE_MINIMAL,
-	SPECTRE_V2_RETPOLINE_MINIMAL_AMD,
 	SPECTRE_V2_RETPOLINE_GENERIC,
 	SPECTRE_V2_RETPOLINE_AMD,
 	SPECTRE_V2_IBRS_ENHANCED,
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -784,8 +784,6 @@ set_mode:
 
 static const char * const spectre_v2_strings[] = {
 	[SPECTRE_V2_NONE]			= "Vulnerable",
-	[SPECTRE_V2_RETPOLINE_MINIMAL]		= "Vulnerable: Minimal generic ASM retpoline",
-	[SPECTRE_V2_RETPOLINE_MINIMAL_AMD]	= "Vulnerable: Minimal AMD ASM retpoline",
 	[SPECTRE_V2_RETPOLINE_GENERIC]		= "Mitigation: Full generic retpoline",
 	[SPECTRE_V2_RETPOLINE_AMD]		= "Mitigation: Full AMD retpoline",
 	[SPECTRE_V2_IBRS_ENHANCED]		= "Mitigation: Enhanced IBRS",
@@ -810,11 +808,6 @@ static void __init spec_v2_print_cond(co
 		pr_info("%s selected on command line.\n", reason);
 }
 
-static inline bool retp_compiler(void)
-{
-	return __is_defined(CONFIG_RETPOLINE);
-}
-
 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 {
 	enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
@@ -912,14 +905,12 @@ retpoline_auto:
 			pr_err("Spectre mitigation: LFENCE not serializing, switching to generic retpoline\n");
 			goto retpoline_generic;
 		}
-		mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
-					 SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
+		mode = SPECTRE_V2_RETPOLINE_AMD;
 		setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
 		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
 	} else {
 	retpoline_generic:
-		mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_GENERIC :
-					 SPECTRE_V2_RETPOLINE_MINIMAL;
+		mode = SPECTRE_V2_RETPOLINE_GENERIC;
 		setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
 	}