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[Xen-devel] [PATCH] xen: xen_init_cpuid_mask: Zero cx before calling xen

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Subject: [Xen-devel] [PATCH] xen: xen_init_cpuid_mask: Zero cx before calling xen_cpuid
From: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Date: Sat, 8 Aug 2009 13:15:00 -0700
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
Delivery-date: Mon, 17 Aug 2009 07:26:41 -0700
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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 
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 <josh@xxxxxxxxxxxxxxxx>

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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