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    Subject[PATCH AUTOSEL 4.19 087/191] x86/CPU: Change query logic so CPUID is enabled before testing
    Date
    From: Matthew Whitehead <tedheadster@gmail.com>

    [ Upstream commit 2893cc8ff892fa74972d8dc0e1d0dc65116daaa3 ]

    Presently we check first if CPUID is enabled. If it is not already
    enabled, then we next call identify_cpu_without_cpuid() and clear
    X86_FEATURE_CPUID.

    Unfortunately, identify_cpu_without_cpuid() is the function where CPUID
    becomes _enabled_ on Cyrix 6x86/6x86L CPUs.

    Reverse the calling sequence so that CPUID is first enabled, and then
    check a second time to see if the feature has now been activated.

    [ bp: Massage commit message and remove trailing whitespace. ]

    Suggested-by: Andy Lutomirski <luto@amacapital.net>
    Signed-off-by: Matthew Whitehead <tedheadster@gmail.com>
    Signed-off-by: Borislav Petkov <bp@suse.de>
    Reviewed-by: Andy Lutomirski <luto@amacapital.net>
    Cc: David Woodhouse <dwmw@amazon.co.uk>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/20180921212041.13096-3-tedheadster@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kernel/cpu/common.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
    index b33fdfa0ff49e..04622625f8e22 100644
    --- a/arch/x86/kernel/cpu/common.c
    +++ b/arch/x86/kernel/cpu/common.c
    @@ -1104,6 +1104,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
    memset(&c->x86_capability, 0, sizeof c->x86_capability);
    c->extended_cpuid_level = 0;

    + if (!have_cpuid_p())
    + identify_cpu_without_cpuid(c);
    +
    /* cyrix could have cpuid enabled via c_identify()*/
    if (have_cpuid_p()) {
    cpu_detect(c);
    @@ -1121,7 +1124,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
    if (this_cpu->c_bsp_init)
    this_cpu->c_bsp_init(c);
    } else {
    - identify_cpu_without_cpuid(c);
    setup_clear_cpu_cap(X86_FEATURE_CPUID);
    }

    --
    2.20.1
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