From: Igor Mammedov <imammedo@redhat.com>
Date: Mon, 10 Jun 2013 16:31:11 +0000 (+0200)
Subject: x86: kvmclock: zero initialize pvclock shared memory area
X-Git-Tag: v3.10-rc7~11^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=07868fc6aaf57847b0f3a3d53086b7556eb83f4a;p=pandora-kernel.git

x86: kvmclock: zero initialize pvclock shared memory area

kernel might hung in pvclock_clocksource_read() due to
uninitialized memory might contain odd version value in
following cycle:

        do {
                version = __pvclock_read_cycles(src, &ret, &flags);
        } while ((src->version & 1) || version != src->version);

if secondary kvmclock is accessed before it's registered with kvm.

Clear garbage in pvclock shared memory area right after it's
allocated to avoid this issue.

Ref: https://bugzilla.kernel.org/show_bug.cgi?id=59521
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
[See BZ for analysis.  We may want a different fix for 3.11, but
 this is the safest for now - Paolo]
Cc: <stable@vger.kernel.org> # 3.8
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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