[Qemu-devel] [PULL v2 16/16] acpi-build: Set FORCE_APIC_CLUSTER_MODEL bit for FADT flags

["Michael S. Tsirkin" <mst@redhat.com>]

From: zhanghailiang <zhang.zhanghailiang@huawei.com>

If we start Windows 2008 R2 DataCenter with number of cpu less than 8,
The system will use APIC Flat Logical destination mode as default configuration,
Which has an upper limit of 8 CPUs.

The fault is that VM can not show all processors within Task Manager if
we hot-add cpus when the number of cpus in VM extends the limit of 8.

If we use cluster destination model, the problem will be solved.

Note:
This flag was introduced later than ACPI v1.0 specification while QEMU
generates v1.0 tables only, but...

linux kernel ignores this flag, so patch has no influence on it.

Tested with Win[XPsp3|Srv2003EE|Srv2008DC|Srv2008R2|Srv2012R2], there
isn't BSODs and guests boot just fine. In cases guest doesn't support
cpu-hotplug, cpu becomes visible after reboot and in case the guest
supports cpu-hotplug, it works as expected with this patch.

Cc: qemu-stable@nongnu.org
Signed-off-by: huangzhichao <huangzhichao@huawei.com>
Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-By: Igor Mammedov <imammedo@redhat.com>
---
 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 3e7fba3..a313321 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -551,6 +551,12 @@ static void fadt_setup(AcpiFadtDescriptorRev1 *fadt, AcpiPmInfo *pm)
                               (1 << ACPI_FADT_F_SLP_BUTTON) |
                               (1 << ACPI_FADT_F_RTC_S4));
     fadt->flags |= cpu_to_le32(1 << ACPI_FADT_F_USE_PLATFORM_CLOCK);
+    /* APIC destination mode ("Flat Logical") has an upper limit of 8 CPUs
+     * For more than 8 CPUs, "Clustered Logical" mode has to be used
+     */
+    if (max_cpus > 8) {
+        fadt->flags |= cpu_to_le32(1 << ACPI_FADT_F_FORCE_APIC_CLUSTER_MODEL);
+    }
 }
 
 
-- 
MST