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Description of problem:

Since the microcode_ctl update you check for 'hypervisor' CPU flag, which means it refuses to apply the update inside of a Xen dom0, which is a type of guest.

This breaks the xen feature ucode=scan which will check the initramfs for the microcode and apply it automatically, which I've been using.

Version-Release number of selected component (if applicable):

microcode_ctl-2.1-29.10.el7_5.x86_64

How reproducible:

100%

Steps to Reproduce:
1. Update microcode_ctl
2. Check initramfs type with 'file' (should be cpio, but will be gzip)

Actual results:

initramfs contains no GenuineIntel.bin

Expected results:

initramfs should contain GenuineIntel.bin on platforms with microcode

Additional info:

I found this check at line 146 of the update_ucode script:

        if grep -q '^flags[[:space:]]*:.*hypervisor' /proc/cpuinfo; then

This check is too broad for Xen.  Might make sense to change this check /sys/hypervisor for values related to Xen.  It looks like /sys/hypervisor/uuid will be '00000000-0000-0000-0000-000000000000' in case it's a dom0 and otherwise populated if it's a domU.

I've been informed that you might also try one of these checks:

1) call systemd-detect-virt

outputs 'none' in dom0
outputs 'xen' in domU
outputs 'kvm' in KVM guest

2) call virt-what

3) check for /proc/xen/capabilities existence

Correction: For option 3) check for /proc/xen/capabilities with 'control_d', not for its existence

Hello.

RHEL 7 kernel doesn't support Xen dom0. As a possible workaround, I can suggest either to update to a kernel that is based on 3.10.0-862.14.1 (or any newer, see additional information in /usr/share/microcode_ctl/ucode_with_caveats/intel/readme), or updating to microcode_ctl-2.1-29.12 (or newer) and enforce addition of intel microcode files to the initramfs by creating /etc/microcode_ctl/ucode_with_caveats/intel-force-early file (see /usr/share/doc/microcode_ctl/README.caveats for details).