Intel Sandy Bridge-E/EN/EP CPU models (SNB-EP, family 6, model 45, stepping 7)
have issues with MDS-related microcode update that may lead to a system hang
after a microcode update. In order to address this, microcode update
to the MDS-related revision 0x718 has been disabled, and the previously
published microcode revision 0x714 is used by default for the OS-driven
microcode update.
 
For the reference, SHA1 checksums of 06-2d-07 microcode files containing
microcode revisions in question are listed below:
 * 06-2d-07, revision 0x714: bcf2173cd3dd499c37defbc2533703cfa6ec2430
 * 06-2d-07, revision 0x718: 837cfebbfc09b911151dfd179082ad99cf87e85d
 
Please contact your system vendor for a BIOS/firmware update that contains
the latest microcode version. For the information regarding microcode versions
required for mitigating specific side-channel cache attacks, please refer
to the following knowledge base articles:
 * CVE-2017-5715 ("Spectre"):
   https://access.redhat.com/articles/3436091
 * CVE-2018-3639 ("Speculative Store Bypass"):
   https://access.redhat.com/articles/3540901
 * CVE-2018-3620, CVE-2018-3646 ("L1 Terminal Fault Attack"):
   https://access.redhat.com/articles/3562741
 * CVE-2018-12130, CVE-2018-12126, CVE-2018-12127, and CVE-2019-11091
   ("Microarchitectural Data Sampling"):
   https://access.redhat.com/articles/4138151
 
The information regarding enforcing microcode load is provided below.
 
To enforce usage of the 0x718 microcode revision for a specific kernel version,
please create file "force-intel-06-2d-07" inside /lib/firmware/<kernel_version>
directory, run "/usr/libexec/microcode_ctl/update_ucode" to add it to firmware
directory where microcode will be available for late microcode update,
and run "dracut -f --kver <kernel_version>", so initramfs for this kernel
version is regenerated and the microcode can be loaded early, for example:
 
    touch /lib/firmware/3.10.0-862.9.1/force-intel-06-2d-07
    /usr/libexec/microcode_ctl/update_ucode
    dracut -f --kver 3.10.0-862.9.1
 
After that, it is possible to perform a late microcode update by executing
"/usr/libexec/microcode_ctl/reload_microcode" or by writing value "1" to
"/sys/devices/system/cpu/microcode/reload" directly.
 
To enforce addition of this microcode for all kernels, please create file
"/etc/microcode_ctl/ucode_with_caveats/force-intel-06-2d-07", run
"/usr/libexec/microcode_ctl/update_ucode" for enabling late microcode updates,
and "dracut -f --regenerate-all" for enabling early microcode updates:
 
    mkdir -p /etc/microcode_ctl/ucode_with_caveats
    touch /etc/microcode_ctl/ucode_with_caveats/force-intel-06-2d-07
    /usr/libexec/microcode_ctl/update_ucode
    dracut -f --regenerate-all
 
Please refer to /usr/share/doc/microcode_ctl/README.caveats for additional
information.