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    Subject[tip:x86/urgent] x86/microcode: Do the family check first
    Commit-ID:  1f161f67a272cc4f29f27934dd3f74cb657eb5c4
    Gitweb: https://git.kernel.org/tip/1f161f67a272cc4f29f27934dd3f74cb657eb5c4
    Author: Borislav Petkov <bp@suse.de>
    AuthorDate: Thu, 12 Oct 2017 13:23:16 +0200
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Sat, 14 Oct 2017 12:55:40 +0200

    x86/microcode: Do the family check first

    On CPUs like AMD's Geode, for example, we shouldn't even try to load
    microcode because they do not support the modern microcode loading
    interface.

    However, we do the family check *after* the other checks whether the
    loader has been disabled on the command line or whether we're running in
    a guest.

    So move the family checks first in order to exit early if we're being
    loaded on an unsupported family.

    Reported-and-tested-by: Sven Glodowski <glodi1@arcor.de>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Cc: <stable@vger.kernel.org> # 4.11..
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://bugzilla.suse.com/show_bug.cgi?id=1061396
    Link: http://lkml.kernel.org/r/20171012112316.977-1-bp@alien8.de
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/kernel/cpu/microcode/core.c | 27 ++++++++++++++++++---------
    1 file changed, 18 insertions(+), 9 deletions(-)

    diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
    index 86e8f0b..c4fa4a8 100644
    --- a/arch/x86/kernel/cpu/microcode/core.c
    +++ b/arch/x86/kernel/cpu/microcode/core.c
    @@ -122,9 +122,6 @@ static bool __init check_loader_disabled_bsp(void)
    bool *res = &dis_ucode_ldr;
    #endif

    - if (!have_cpuid_p())
    - return *res;
    -
    /*
    * CPUID(1).ECX[31]: reserved for hypervisor use. This is still not
    * completely accurate as xen pv guests don't see that CPUID bit set but
    @@ -166,24 +163,36 @@ bool get_builtin_firmware(struct cpio_data *cd, const char *name)
    void __init load_ucode_bsp(void)
    {
    unsigned int cpuid_1_eax;
    + bool intel = true;

    - if (check_loader_disabled_bsp())
    + if (!have_cpuid_p())
    return;

    cpuid_1_eax = native_cpuid_eax(1);

    switch (x86_cpuid_vendor()) {
    case X86_VENDOR_INTEL:
    - if (x86_family(cpuid_1_eax) >= 6)
    - load_ucode_intel_bsp();
    + if (x86_family(cpuid_1_eax) < 6)
    + return;
    break;
    +
    case X86_VENDOR_AMD:
    - if (x86_family(cpuid_1_eax) >= 0x10)
    - load_ucode_amd_bsp(cpuid_1_eax);
    + if (x86_family(cpuid_1_eax) < 0x10)
    + return;
    + intel = false;
    break;
    +
    default:
    - break;
    + return;
    }
    +
    + if (check_loader_disabled_bsp())
    + return;
    +
    + if (intel)
    + load_ucode_intel_bsp();
    + else
    + load_ucode_amd_bsp(cpuid_1_eax);
    }

    static bool check_loader_disabled_ap(void)
    \
     
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