[Qemu-devel] [PATCH for-3.0 v2] pc: acpi: fix memory hotplug regression by reducing stub SRAT entry size

[Igor Mammedov <imammedo@redhat.com>]

Commit 848a1cc1e (hw/acpi-build: build SRAT memory affinity structures for DIMM devices)
broke the first dimm hotplug in following cases:

 1: there is no coldplugged dimm in the last numa node
    but there is a coldplugged dimm in another node

  -m 4096,slots=4,maxmem=32G               \
  -object memory-backend-ram,id=m0,size=2G \
  -device pc-dimm,memdev=m0,node=0         \
  -numa node,nodeid=0                      \
  -numa node,nodeid=1

 2: if order of dimms on CLI is:
       1st plugged dimm in node1
       2nd plugged dimm in node0

  -m 4096,slots=4,maxmem=32G               \
  -object memory-backend-ram,size=2G,id=m0 \
  -device pc-dimm,memdev=m0,node=1         \
  -object memory-backend-ram,id=m1,size=2G \
  -device pc-dimm,memdev=m1,node=0         \
  -numa node,nodeid=0                      \
  -numa node,nodeid=1

(qemu) object_add memory-backend-ram,id=m2,size=1G
(qemu) device_add pc-dimm,memdev=m2,node=0

the first DIMM hotplug to any node except the last one
fails (Windows is unable to online it).

Length reduction of stub hotplug memory SRAT entry,
fixes issue for some reason.

RHBZ: 1609234

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
NOTE TO MAINTAINER: UPDATE REFERENCE APCI TABLE BLOBS

v2:
 fixup examples in commit message
 (they were in wrong order and with duplicate memdev=m1)
---
 hw/i386/acpi-build.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 9e8350c..b52fdb2 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -2269,7 +2269,16 @@ static void build_srat_hotpluggable_memory(GArray *table_data, uint64_t base,
         numamem = acpi_data_push(table_data, sizeof *numamem);
 
         if (!info) {
-            build_srat_memory(numamem, cur, end - cur, default_node,
+            /*
+             * Entry is required for Windows to enable memory hotplug in OS
+             * and for Linux to enable SWIOTLB when booted with less than
+             * 4G of RAM. Windows works better if the entry sets proximity
+             * to the highest NUMA node in the machine at the end of the
+             * reserved space.
+             * Memory devices may override proximity set by this entry,
+             * providing _PXM method if necessary.
+             */
+            build_srat_memory(numamem, end - 1, 1, default_node,
                               MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED);
             break;
         }
@@ -2402,14 +2411,6 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
         build_srat_memory(numamem, 0, 0, 0, MEM_AFFINITY_NOFLAGS);
     }
 
-    /*
-     * Entry is required for Windows to enable memory hotplug in OS
-     * and for Linux to enable SWIOTLB when booted with less than
-     * 4G of RAM. Windows works better if the entry sets proximity
-     * to the highest NUMA node in the machine.
-     * Memory devices may override proximity set by this entry,
-     * providing _PXM method if necessary.
-     */
     if (hotplugabble_address_space_size) {
         build_srat_hotpluggable_memory(table_data, machine->device_memory->base,
                                        hotplugabble_address_space_size,
-- 
2.7.4