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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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