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microcode_ctl add missing readme source 

Signed-off-by: basebuilder_pel7ppc64lebuilder0 <basebuilder@powerel.org>
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basebuilder_pel7ppc64lebuilder0 2019-11-25 09:33:50 +01:00
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Intel Sandy Bridge-E/EN/EP (SNB-EP, family 6, model 45, stepping 7) has 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 this microcode revision, please create a 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 3.10.0-862.9.1", so initramfs for this version
is regenerated and the microcode can be loaded early:

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 a 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.