Hi ACPI maintainers, I'm reporting a reproducible ACPI MADT/APIC firmware bug on the MiTAC PH12LI motherboard (Intel i7-4770TE), where the BIOS fails to enumerate all LAPIC entries when Hyper-Threading is enabled. Summary: - BIOS exposes only 4 LAPIC entries in MADT - SSDTs declare all 8 logical CPUs (0-7) - Linux kernel fails to initialize HT siblings or behaves erratically I have validated and resolved the issue by: - Rebuilding a corrected MADT with 8 LAPIC entries - Overriding via initramfs (`apic.aml`) using `acpi_apic_instance=1 acpi_override` - Verifying proper CPU/IRQ behavior across reboots [[UPDATE]] MiTac issued a BIOS firmware update in 2019, but I had to contact to OEM to get it. This fix may work for other Haswell era processors, since the firmware is of course system specific, so I will leave it up. If someone can confirm whether this works on another Haswell system, that would be great. The override project is documented here: https://github.com/michalkrupa/rhel-kernel-bugfix Would this warrant a known-DMI quirk, or a documentation mention for kernel/firmware compatibility? Best, Michal Krupa
