The recent fix to ignore invalid x2APIC entries inadvertently broke systems with creative MADT APIC tables. The affected systems have APIC MADT tables where all entries have invalid APIC IDs (0xFF), which means they register exactly zero CPUs. But the condition to ignore the entries of APIC IDs < 255 in the X2APIC MADT table is solely based on the count of MADT APIC table entries. As a consequence, the affected machines enumerate no secondary CPUs at all because the APIC table has entries and therefore the X2APIC table entries with APIC IDs < 255 are ignored. Change the condition so that the APIC table preference for APIC IDs < 255 only becomes effective when the APIC table has valid APIC ID entries. IOW, an APIC table full of invalid APIC IDs is considered to be empty which in consequence enables the X2APIC table entries with a APIC ID < 255 and restores the expected behaviour.
Unified · Split
| @@ -293,6 +293,7 @@ acpi_parse_lapic(union acpi_subtable_headers * header, const unsigned long end) · 292 unmodified lines | ||
| 293 | 293 | processor->processor_id, /* ACPI ID */ |
| 294 | 294 | processor->lapic_flags & ACPI_MADT_ENABLED); |
| 295 | 295 | |
| 296 | + has_lapic_cpus = true; | |
| 296 | 297 | return 0; |
| 297 | 298 | } |
| 298 | 299 | |
| @@ -1134,7 +1135,6 @@ static int __init acpi_parse_madt_lapic_entries(void) · 835 unmodified lines | ||
| 1134 | 1135 | if (!count) { |
| 1135 | 1136 | count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC, |
| 1136 | 1137 | acpi_parse_lapic, MAX_LOCAL_APIC); |
| 1137 | − has_lapic_cpus = count > 0; | |
| 1138 | 1138 | x2count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_X2APIC, |
| 1139 | 1139 | acpi_parse_x2apic, MAX_LOCAL_APIC); |
| 1140 | 1140 | } |