From ed2ef10c0ce2feed9647b9f5c3df624078dd2dd0 Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Fri, 26 Feb 2016 14:59:27 +0100 Subject: [PATCH] pc: acpi: clarify why possible LAPIC entries must be present in MADT Signed-off-by: Igor Mammedov Reviewed-by: Eduardo Habkost Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/i386/acpi-build.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c index 8736917f0b..0a5acb3828 100644 --- a/hw/i386/acpi-build.c +++ b/hw/i386/acpi-build.c @@ -360,6 +360,12 @@ build_madt(GArray *table_data, GArray *linker, PCMachineState *pcms) if (apic_ids->cpus[i].cpu != NULL) { apic->flags = cpu_to_le32(1); } else { + /* ACPI spec says that LAPIC entry for non present + * CPU may be omitted from MADT or it must be marked + * as disabled. However omitting non present CPU from + * MADT breaks hotplug on linux. So possible CPUs + * should be put in MADT but kept disabled. + */ apic->flags = cpu_to_le32(0); } } -- 2.11.0