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Intel Skylake Scalable Platform CPU models that belong to Workstation and HEDT
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(Basin Falls) segment (SKL-W/X, family 6, model 85, stepping 4) had reports
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of system hangs on reboot when revision 0x2000065 of microcode, that was included
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from microcode-20191112 update up to microcode-20200520 update, was applied[1].
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In order to address this, microcode update to the newer revision had been
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disabled by default on these systems, and the previously published microcode
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revision 0x2000064 is used by default for the OS-driven microcode update.
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Since revision 0x2006906 (included with the microcode-20200609 release)
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it is reported that the issue is no longer present, so the newer microcode
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revision is enabled by default now (but can be disabled explicitly; see below).
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[1] https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/21
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For the reference, SHA1 checksums of 06-55-04 microcode files containing
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microcode revisions in question are listed below:
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* 06-55-04, revision 0x2000064: 2e405644a145de0f55517b6a9de118eec8ec1e5a
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* 06-55-04, revision 0x2000065: f27f12b9d53f492c297afd856cdbc596786fad23
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* 06-55-04, revision 0x2006906: 5f18f985f6d5ad369b5f6549b7f3ee55acaef967
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* 06-55-04, revision 0x2006a08: 4059fb1f60370297454177f63cd7cc20b3fa1212
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* 06-55-04, revision 0x2006a0a: 7ec27025329c82de9553c14a78733ad1013e5462
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* 06-55-04, revision 0x2006b06: cb5bec976cb9754e3a22ab6828b3262a8f9eccf7
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Please contact your system vendor for a BIOS/firmware update that contains
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the latest microcode version. For the information regarding microcode versions
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required for mitigating specific side-channel cache attacks, please refer
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to the following knowledge base articles:
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* CVE-2017-5715 ("Spectre"):
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https://access.redhat.com/articles/3436091
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* CVE-2018-3639 ("Speculative Store Bypass"):
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https://access.redhat.com/articles/3540901
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* CVE-2018-3620, CVE-2018-3646 ("L1 Terminal Fault Attack"):
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https://access.redhat.com/articles/3562741
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* CVE-2018-12130, CVE-2018-12126, CVE-2018-12127, and CVE-2019-11091
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("Microarchitectural Data Sampling"):
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https://access.redhat.com/articles/4138151
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* CVE-2019-0117 (Intel SGX Information Leak),
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CVE-2019-0123 (Intel SGX Privilege Escalation),
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CVE-2019-11135 (TSX Asynchronous Abort),
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CVE-2019-11139 (Voltage Setting Modulation):
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https://access.redhat.com/solutions/2019-microcode-nov
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* CVE-2020-0543 (Special Register Buffer Data Sampling),
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CVE-2020-0548 (Vector Register Data Sampling),
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CVE-2020-0549 (L1D Cache Eviction Sampling):
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https://access.redhat.com/solutions/5142751
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* CVE-2020-8695 (Information disclosure issue in Intel SGX via RAPL interface),
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CVE-2020-8696 (Vector Register Leakage-Active),
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CVE-2020-8698 (Fast Forward Store Predictor):
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https://access.redhat.com/articles/5569051
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* CVE-2020-24489 (VT-d-related Privilege Escalation),
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CVE-2020-24511 (Improper Isolation of Shared Resources),
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CVE-2020-24512 (Observable Timing Discrepancy),
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CVE-2020-24513 (Information Disclosure on Some Intel Atom Processors):
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https://access.redhat.com/articles/6101171
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The information regarding disabling microcode update is provided below.
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To disable usage of the newer microcode revision for a specific kernel
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version, please create a file "disallow-intel-06-55-04" inside
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/lib/firmware/<kernel_version> directory, run
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"/usr/libexec/microcode_ctl/update_ucode" to update firmware directory
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used for late microcode updates, and run "dracut -f --kver <kernel_version>"
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so initramfs for this kernel version is regenerated, for example:
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touch /lib/firmware/3.10.0-862.9.1/disallow-intel-06-55-04
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/usr/libexec/microcode_ctl/update_ucode
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dracut -f --kver 3.10.0-862.9.1
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To disable usage of the newer microcode revision for all kernels, please create
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file "/etc/microcode_ctl/ucode_with_caveats/disallow-intel-06-55-04", run
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"/usr/libexec/microcode_ctl/update_ucode" to update firmware directories
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used for late microcode updates, and run "dracut -f --regenerate-all"
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so initramfs images get regenerated, for example:
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mkdir -p /etc/microcode_ctl/ucode_with_caveats
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touch /etc/microcode_ctl/ucode_with_caveats/disallow-intel-06-55-04
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/usr/libexec/microcode_ctl/update_ucode
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dracut -f --regenerate-all
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Please refer to /usr/share/doc/microcode_ctl/README.caveats for additional
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information.
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