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Bug 1833037 - [RHEL 7] Narrow down the SKX (SKL-SP/X/W/D) microcode blacklist
Summary: [RHEL 7] Narrow down the SKX (SKL-SP/X/W/D) microcode blacklist
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: microcode_ctl
Version: 7.9
Hardware: x86_64
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Eugene Syromiatnikov
QA Contact: Jeff Bastian
URL:
Whiteboard:
Depends On:
Blocks: 1788592
TreeView+ depends on / blocked
 
Reported: 2020-05-07 17:14 UTC by Eugene Syromiatnikov
Modified: 2020-09-29 20:13 UTC (History)
1 user (show)

Fixed In Version: microcode_ctl-2.1-65.el7
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed: 2020-09-29 20:12:29 UTC
Target Upstream Version:
Embargoed:

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2020:3968 0 None None None 2020-09-29 20:13:05 UTC

Description Eugene Syromiatnikov 2020-05-07 17:14:55 UTC 
Currently, due to [1], all microcode updates past revision 0x2000064 are disabled on SKX (1st generation Xeon Skalable Platform, Skylake Scalable Platform, SKL-SP, SKL-X, SKL-W, SKL-D; FF-MM-SS 06-55-04, CPUID 0x50654) by default.  This, in fact, too broad blacklist, as the issue affects only Workstation (SKL-W, SKX-W) and HEDT (SKL-X, SKX-X, Basin Falls) segments.  As it was suggested quite some time ago, these can be differentiated by referring to bits 5..3 of CAPID0 field of PCU registers device (Bus 1, Device 30, Function 3, VID:DID 8086:2083)[2] (there's some information regarding the device's fields available for BDX[3], but not for SKX[4], and they are indeed different).  By implementing a more precise filter, it is possible to avoid issues with the latest CPU errata/CVEs not being mitigated by default in a more common SKL-SP server segment CPU case.

Steps to Reproduce:
1. Install microcode_ctl package, version 2.1-61.el7 or higher on a system with SKL-SP Server segment CPU (Intel Xeon 81xx).
2. Check the dmesg/syslog for disclaimers
3. Check the microcode version populated in /lib/firmware/KERNEL_VERSION/inte-ucode and the early initramfs

Actual results:
Disclaimer is present, older (0x2000064) microcode revision is used.

Expected results:
No disclaimer present, newer (0x2000065) microcode revision is used.

[1] https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/21
[2] https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/xeon-scalable-spec-update.pdf#page
[3] https://www.intel.com/content/www/us/en/processors/xeon/xeon-e5-v4-datasheet-vol-2.html , page 82
[4] https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/2nd-gen-xeon-scalable-spec-update.pdf , page 57
Comment 6 Jeff Bastian 2020-06-29 19:30:10 UTC 
Revision 0x2006906 of the microcode for 06-55-04 CPUs fixes the hanging problems, so this change was undone [*] and this CPU is no longer blacklisted.  The updated microcode revision is available in microcode_ctl-2.1-73.el7; see bug 1826589.

[*] http://pkgs.devel.redhat.com/cgit/rpms/microcode_ctl/commit/?h=rhel-7.9&id=2e60d157a329
Comment 7 Jeff Bastian 2020-06-29 19:31:50 UTC 
Oops, forgot the link to the Beaker job where 06-55-04 was successfully updated to microcode revision 0x2006906 by default:

https://beaker.engineering.redhat.com/recipes/8478436#task112216361
Comment 9 errata-xmlrpc 2020-09-29 20:12:29 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (microcode_ctl bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:3968
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