hw/acpi-build: Add a check for memory-less NUMA nodes

Currently, Qemu ACPI builder doesn't consider the memory-less NUMA nodes, eg:

  -m 4G,slots=4,maxmem=8G \
  -numa node,nodeid=0 \
  -numa node,nodeid=1,mem=2G \
  -numa node,nodeid=2,mem=2G \
  -numa node,nodeid=3\

Guest Linux will report

  [    0.000000] ACPI: SRAT: Node 0 PXM 0 [mem 0x00000000-0xffffffffffffffff]
  [    0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x00000000-0x0009ffff]
  [    0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x00100000-0x7fffffff]
  [    0.000000] ACPI: SRAT: Node 2 PXM 2 [mem 0x80000000-0xbfffffff]
  [    0.000000] ACPI: SRAT: Node 2 PXM 2 [mem 0x100000000-0x13fffffff]
  [    0.000000] ACPI: SRAT: Node 3 PXM 3 [mem 0x140000000-0x13fffffff]
  [    0.000000] ACPI: SRAT: Node 3 PXM 3 [mem 0x140000000-0x33fffffff] hotplug

[mem 0x00000000-0xffffffffffffffff] and [mem 0x140000000-0x13fffffff] are bogus.

Add a check to avoid building srat memory for memory-less NUMA nodes, also update
the test file. Now the info in guest linux will be

  [    0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x00000000-0x0009ffff]
  [    0.000000] ACPI: SRAT: Node 1 PXM 1 [mem 0x00100000-0x7fffffff]
  [    0.000000] ACPI: SRAT: Node 2 PXM 2 [mem 0x80000000-0xbfffffff]
  [    0.000000] ACPI: SRAT: Node 2 PXM 2 [mem 0x100000000-0x13fffffff]
  [    0.000000] ACPI: SRAT: Node 3 PXM 3 [mem 0x140000000-0x33fffffff] hotplug
Signed-off-by: NDou Liyang <douly.fnst@cn.fujitsu.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

hw/i386/acpi-build.c

@@ -2392,9 +2392,12 @@ build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
             mem_len = next_base - pcms->below_4g_mem_size;
             next_base = mem_base + mem_len;
         }
-        numamem = acpi_data_push(table_data, sizeof *numamem);
-        build_srat_memory(numamem, mem_base, mem_len, i - 1,
-                          MEM_AFFINITY_ENABLED);
+
+        if (mem_len > 0) {
+            numamem = acpi_data_push(table_data, sizeof *numamem);
+            build_srat_memory(numamem, mem_base, mem_len, i - 1,
+                              MEM_AFFINITY_ENABLED);
+        }
     }
     slots = (table_data->len - numa_start) / sizeof *numamem;
     for (; slots < pcms->numa_nodes + 2; slots++) {