From db561e6e3910b25d9314ba8b343c4387396c2f3f Mon Sep 17 00:00:00 2001 From: Werner Zeh Date: Tue, 19 Feb 2019 13:39:56 +0100 Subject: [PATCH] acpi: Sort the reported APIC-IDs in the MADT table coreboot performs MP-Init in a parallel way. That leads to the fact that the order, in which the CPUs are woken up, can vary from boot to boot. The creation of the MADT table just parses the devicetree and takes the CPUs reported there as it is for creating the single local APIC entries. Therefore, the OS will see different order of CPUs. There are CPUs out there (like Apollo Lake for example) which have shared caches on core-level and if the order is random this can end up in assigning cores to different tasks or even OSes (in a virtual environment) which uses the same cache. This in turn will produce performance penalties across these distributed tasks/OSes. Though there is a way to discover the core- and cache-topology it will in the end be necessary to take the APIC-ID into account. To simplify it, one can achieve the same output by sorting the APIC-IDs in an ascending order. This will lead to the fact that CPUs that share a given cache will be reported right next to each other in the MADT. Change-Id: Ida74f9f00a4e2a03107a2124014403de60462735 Signed-off-by: Werner Zeh Reviewed-on: https://review.coreboot.org/c/31545 Tested-by: build bot (Jenkins) Reviewed-by: Patrick Georgi Reviewed-by: Paul Menzel --- src/arch/x86/acpi.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/src/arch/x86/acpi.c b/src/arch/x86/acpi.c index f4c7d86dc0..e06c3ad71b 100644 --- a/src/arch/x86/acpi.c +++ b/src/arch/x86/acpi.c @@ -8,7 +8,7 @@ * Copyright (C) 2005-2009 coresystems GmbH * Copyright (C) 2015 Timothy Pearson , * Raptor Engineering - * Copyright (C) 2016-2017 Siemens AG + * Copyright (C) 2016-2019 Siemens AG * * ACPI FADT, FACS, and DSDT table support added by * Nick Barker , and those portions @@ -48,6 +48,7 @@ #include #include #include +#include u8 acpi_checksum(u8 *table, u32 length) { @@ -149,7 +150,7 @@ int acpi_create_madt_lapic(acpi_madt_lapic_t *lapic, u8 cpu, u8 apic) unsigned long acpi_create_madt_lapics(unsigned long current) { struct device *cpu; - int index = 0; + int index, apic_ids[CONFIG_MAX_CPUS], num_cpus = 0; for (cpu = all_devices; cpu; cpu = cpu->next) { if ((cpu->path.type != DEVICE_PATH_APIC) || @@ -158,9 +159,14 @@ unsigned long acpi_create_madt_lapics(unsigned long current) } if (!cpu->enabled) continue; + if (num_cpus >= ARRAY_SIZE(apic_ids)) + break; + apic_ids[num_cpus++] = cpu->path.apic.apic_id; + } + bubblesort(apic_ids, num_cpus, NUM_ASCENDING); + for (index = 0; index < num_cpus; index++) { current += acpi_create_madt_lapic((acpi_madt_lapic_t *)current, - index, cpu->path.apic.apic_id); - index++; + index, apic_ids[index]); } return current;