CVE-2017-5753
CVE-2017-5715

In order to reduce the impact of using MFENCE, make the execution of the
LFENCE instruction serialized.  This is done by setting bit 1 of MSR
0xc0011029 (DE_CFG).

Some families that support LFENCE do not have this MSR.  For these
families, the LFENCE instruction is already serialized.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
(backported from commit c8bd06975d1b15b5f81f684d9d3f926b60cd77a9)
Signed-off-by: Andy Whitcroft <apw@canonical.com>