[PATCH v3 5/5] hw/mips/malta: Verify malta-strict machine uses correct DIMM sizes

[Philippe Mathieu-Daudé]

The machine has 4 DIMM slots. Each DIMM must be a power of 2.
Add a check the total RAM is a good combination of DIMMs.

Example when asking a combination not power of 2:

  $ qemu-system-mips -M malta-strict -bios /dev/null -m 252
  qemu-system-mips: RAM size must be the combination of 4 powers of 2

Working example (as 100 = 64 + 32 + 2 + 2):

  $ qemu-system-mips -M malta-strict -monitor stdio -S -bios /dev/null -m 100
  QEMU 5.0.50 monitor - type 'help' for more information
  (qemu) info mtree
  address-space: memory
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      0000000000000000-00000000063fffff (prio 0, ram): alias 
mips_malta_low_preio.ram @mips_malta.ram 0000000000000000-00000000063fffff

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/mips/malta.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/mips/malta.c b/hw/mips/malta.c
index ac4a618751..17f5833a94 100644
--- a/hw/mips/malta.c
+++ b/hw/mips/malta.c
@@ -71,6 +71,8 @@
 
 #define MAX_IDE_BUS         2
 
+#define DIMM_SLOTS_COUNT    4
+
 #define TYPE_MALTA_MACHINE       MACHINE_TYPE_NAME("malta-base")
 #define MALTA_MACHINE_CLASS(klass) \
      OBJECT_CLASS_CHECK(MaltaMachineClass, (klass), TYPE_MALTA_MACHINE)
@@ -82,6 +84,7 @@ typedef struct MaltaMachineClass {
     MachineClass parent_obj;
     /* Public */
     ram_addr_t max_ramsize;
+    bool verify_dimm_sizes;
 } MaltaMachineClass;
 
 typedef struct {
@@ -1260,6 +1263,12 @@ void mips_malta_init(MachineState *machine)
     /* create CPU */
     mips_create_cpu(machine, s, &cbus_irq, &i8259_irq);
 
+    if (mmc->verify_dimm_sizes && ctpop64(ram_size) > DIMM_SLOTS_COUNT) {
+        error_report("RAM size must be the combination of %d powers of 2",
+                     DIMM_SLOTS_COUNT);
+        exit(1);
+    }
+
     /*
      * The GT-64120A north bridge accepts at most 256 MiB per SCS for
      * address decoding, so we have a maximum of 1 GiB. We deliberately
@@ -1493,6 +1502,7 @@ static void malta_machine_strict_class_init(ObjectClass 
*oc, void *data)
 #endif
     mc->default_ram_size = 32 * MiB;
     mmc->max_ramsize = 256 * MiB; /* 32 MByte PC100 SDRAM DIMMs x 4 slots */
+    mmc->verify_dimm_sizes = true;
 };
 
 static const TypeInfo malta_machine_types[] = {
-- 
2.21.3