[Qemu-devel] [PATCH v6 1/4] hw/acpi-build: Fix SRAT memory building in case of node 0 without RAM

[Dou Liyang]

From: Eduardo Habkost <address@hidden>

Currently, Using the fisrt node without memory on the machine makes
QEMU unhappy. With this example command line:
  ... \
  -m 1024M,slots=4,maxmem=32G \
  -numa node,nodeid=0 \
  -numa node,mem=1024M,nodeid=1 \
  -numa node,nodeid=2 \
  -numa node,nodeid=3 \
Guest reports "No NUMA configuration found" and the NUMA topology is
wrong.

This is because when QEMU builds ACPI SRAT, it regards node 0 as the
default node to deal with the memory hole(640K-1M). this means the
node0 must have some memory(>1M), but, actually it can have no
memory.

Fix this problem by cut out the 640K hole in the same way the PCI
4G hole does.

Signed-off-by: Eduardo Habkost <address@hidden>
Signed-off-by: Dou Liyang <address@hidden>
---
 hw/i386/acpi-build.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 98dd424..a0cf3bf 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -2318,6 +2318,9 @@ build_tpm2(GArray *table_data, BIOSLinker *linker)
                  (void *)tpm2_ptr, "TPM2", sizeof(*tpm2_ptr), 4, NULL, NULL);
 }
 
+#define HOLE_640K_START  (640 * 1024)
+#define HOLE_640K_END   (1024 * 1024)
+
 static void
 build_srat(GArray *table_data, BIOSLinker *linker, MachineState *machine)
 {
@@ -2373,17 +2376,30 @@ build_srat(GArray *table_data, BIOSLinker *linker, 
MachineState *machine)
     next_base = 0;
     numa_start = table_data->len;
 
-    numamem = acpi_data_push(table_data, sizeof *numamem);
-    build_srat_memory(numamem, 0, 640 * 1024, 0, MEM_AFFINITY_ENABLED);
-    next_base = 1024 * 1024;
     for (i = 1; i < pcms->numa_nodes + 1; ++i) {
         mem_base = next_base;
         mem_len = pcms->node_mem[i - 1];
-        if (i == 1) {
-            mem_len -= 1024 * 1024;
-        }
         next_base = mem_base + mem_len;
 
+        /* Cut out the 640K hole */
+        if (mem_base <= HOLE_640K_START &&
+            next_base > HOLE_640K_START) {
+            mem_len -= next_base - HOLE_640K_START;
+            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);
+            }
+
+            /* Check for the rare case: 640K < RAM < 1M */
+            if (next_base <= HOLE_640K_END) {
+                next_base = HOLE_640K_END;
+                continue;
+            }
+            mem_base = HOLE_640K_END;
+            mem_len = next_base - HOLE_640K_END;
+        }
+
         /* Cut out the ACPI_PCI hole */
         if (mem_base <= pcms->below_4g_mem_size &&
             next_base > pcms->below_4g_mem_size) {
-- 
2.5.5