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    Subject[PATCH] xen: xen_init_cpuid_mask: Zero cx before calling xen_cpuid
    CPUID function 1 doesn't use cx, but xen_cpuid doesn't know that,
    resulting in this warning:

    arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
    arch/x86/xen/enlighten.c:192: warning: ‘cx’ may be used uninitialized in this function
    arch/x86/xen/enlighten.c:205: note: ‘cx’ was declared here

    Set cx = 0 to avoid this warning. This seems preferable to implementing
    a xen_cpuid_nocount without the input constraint for cx, and either of
    those seem preferable to just ignoring the warning.

    Signed-off-by: Josh Triplett <>

    Build-tested only.

    arch/x86/xen/enlighten.c | 1 +
    1 files changed, 1 insertions(+), 0 deletions(-)

    diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
    index 0a1700a..6ee2ef8 100644
    --- a/arch/x86/xen/enlighten.c
    +++ b/arch/x86/xen/enlighten.c
    @@ -215,6 +215,7 @@ static __init void xen_init_cpuid_mask(void)
    (1 << X86_FEATURE_ACPI)); /* disable ACPI */

    ax = 1;
    + cx = 0;
    xen_cpuid(&ax, &bx, &cx, &dx);

    /* cpuid claims we support xsave; try enabling it to see what happens */
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      Last update: 2009-08-08 22:17    [W:0.032 / U:17.348 seconds]
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