On Fri, Jul 28 2023 at 16:47, Rui Zhang wrote: > On Fri, 2023-07-28 at 14:51 +0200, Thomas Gleixner wrote: >> As the call sites during MADT parsing ignore the return value anyway, >> there is no harm and this is a proper defense against broken tables >> which enumerate an APIC twice. > > Yeah, this can fix the duplicate APIC ID issue. We want it independent of the below. > But for x2APIC CPUs with unique APIC ID, but smaller than 255, should > we still enumerate them when we already have valid LAPIC entries? > > For the Ivebridge-EP 2-socket system, > > LAPIC: APIC ID from 0x0 - 0xB, 0x10 - 0x1B, 0x20 - 0x2B, 0x30 - 0x3B > x2APIC: APIC ID from 0x0 - 0x77 > > # cpuid -1 -l 0xb -s 1 > CPU: > --- level 1 (core) --- > bits to shift APIC ID to get next = 0x5 (5) > logical processors at this level = 0x18 (24) > level number = 0x1 (1) > level type = core (2) > extended APIC ID = 0 > > If we still enumerates all the x2APIC entries, > 1. we got 72 extra possible CPUs from x2APIC > 2. with the patch at https://lore.kernel.org/all/87edm36qqb.ffs@tglx/ , > _max_logical_packages is set to 4 instead of 2. > > this is still a problem, right? Yes, you are right. But I still don't like the indirection of the returned CPU number. It's an ACPI selfcontained issue, no? So something like this should do the trick: + count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC, + acpi_parse_lapic, MAX_LOCAL_APIC); + if (count) + has_lapic_cpus = true; + x2count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_X2APIC, + acpi_parse_x2apic, MAX_LOCAL_APIC); } if (!count && !x2count) { pr_err("No LAPIC entries present\n");
