EC2 t3.small
Fedora CoreOS stable 31.20200310.3.0

CoreOS incorrectly reports CPU info via /proc/cpuinfo #413

jlebon commented

Likely due to FCOS disabling SMT when necessary: https://github.com/coreos/fedora-coreos-tracker/blob/master/Design.md#automatically-disable-smt-when-needed-to-address-vulnerabilities.
I'm guessing the vCPUs count quoted in EC2 instance types assume hyperthreading.

cyrus-mc commented

That appears to be it. Appreciate the quick response.

I updated the kernel options using

rpm-ostree kargs --replace="mitigations=auto"
Removing nosmt.

# CPU ごとのコア数
grep cpu.cores /proc/cpuinfo

# 実行結果
cpu cores   : 1

# カーネルオプションを更新
sudo rpm-ostree kargs --replace="mitigations=auto"

Staging deployment... done
Kernel arguments updated.
Run "systemctl reboot" to start a reboot

# 再起動
sudo systemctl reboot

# 再起動後
# CPU ごとのコア数
grep cpu.cores /proc/cpuinfo

# 実行結果
cpu cores   : 1
cpu cores   : 1