OK, as expected linux-firmware upgrade seems to be unrelated. After doing more than two dozen shutdowns with each kernel (4.15.0-10 and 4.15.0-12) I see the following pattern:
* secure boot enabled or disabled makes no difference * kernel 4.15.0-10 correctly powers off system (halt -p) every time, power source makes no difference * kernel 4.15.0-12 correctly powers off system only when running on AC * kernel 4.15.0-12 does NOT power off system (reboots instead) when AC power is NOT connected (running on battery) every time ** Summary changed: - Kernel 4.15.0-12 reboots instead of turning off on HP Spectre x360 13-ae004 + Kernel 4.15.0-12 reboots instead of turning off on HP Spectre x360 13-ae004 on battery -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-signed in Ubuntu. https://bugs.launchpad.net/bugs/1756455 Title: Kernel 4.15.0-12 reboots instead of turning off on HP Spectre x360 13-ae004 on battery Status in linux-signed package in Ubuntu: New Bug description: Ubuntu 18.04, installed from beta 1 ISO + all updates to date HP Spectre x360 13", model 13-ae004na, secure boot on, latest BIOS F.15A, Ubuntu is the only system on disk. When using kernel 4.15.0-12 the system does not power off but instead reboots. Both halt -p from the command line and menu action leads to reboot. Booting with previous kernel 4.15.0-10 resolves the issue, system turns off power as expected. I am not attaching any logs because I cannot see anything unusual there, kern.log entries from 4.15.0-10 and 4.15.0-12 seems to be identical (in fact, there is only one entry there "msr: Direct access to MSR 1b0"). Please let me know what additional information you may need. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-signed/+bug/1756455/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp