[Qemu-devel] [PATCH v2 09/10] pc: acpi: clarify why possible LAPIC entries must be present in MADT

[Igor Mammedov]

Signed-off-by: Igor Mammedov <address@hidden>
Reviewed-by: Eduardo Habkost <address@hidden>
---
 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 6ac05b3..5fc8019 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -363,6 +363,12 @@ build_madt(GArray *table_data, GArray *linker, 
MachineState *machine)
         if (id.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);
         }
     }
-- 
1.8.3.1