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    Subject[PATCH 4.14 079/146] x86/retpoline: Remove minimal retpoline support
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Zhenzhong Duan zhenzhong.duan@oracle.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@infradead.org>
    Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: David Woodhouse <dwmw@amazon.co.uk>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: <srinivas.eeda@oracle.com>
    Cc: stable@vger.kernel.org
    Link: https://lkml.kernel.org/r/f06f0a89-5587-45db-8ed2-0a9d6638d5c0@default
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/include/asm/nospec-branch.h | 3 ---
    arch/x86/kernel/cpu/bugs.c | 13 ++-----------
    2 files changed, 2 insertions(+), 14 deletions(-)

    --- a/arch/x86/include/asm/nospec-branch.h
    +++ b/arch/x86/include/asm/nospec-branch.h
    @@ -221,11 +221,8 @@
    /* 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,
    SPECTRE_V2_IBRS_ENHANCED,
    };

    --- a/arch/x86/kernel/cpu/bugs.c
    +++ b/arch/x86/kernel/cpu/bugs.c
    @@ -134,8 +134,6 @@ enum spectre_v2_mitigation_cmd {

    static const char *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",
    @@ -249,11 +247,6 @@ static void __init spec2_print_if_secure
    pr_info("%s selected on command line.\n", reason);
    }

    -static inline bool retp_compiler(void)
    -{
    - return __is_defined(CONFIG_RETPOLINE);
    -}
    -
    static inline bool match_option(const char *arg, int arglen, const char *opt)
    {
    int len = strlen(opt);
    @@ -414,14 +407,12 @@ 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);
    }


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