[Qemu-devel] [PATCH v2 2/2] hw/arm/virt: don't use a15memmap directly

[Andrew Jones <drjones@redhat.com>]

We should always go through VirtBoardInfo when we need the memmap.
To avoid using a15memmap directly, in this case, we need to defer
the max-cpus check from class init time to instance init time. In
class init we now use MAX_CPUMASK_BITS for max_cpus initialization,
which is the maximum QEMU supports, and also, incidentally, the
maximum KVM/gicv3 currently supports. Also, a nice side-effect of
delaying the max-cpus check is that we now get more appropriate
error messages for gicv2 machines that try to configure more than
123 cpus. Before this patch it would complain that the requested
number of cpus was greater than 123, but for gicv2 configs, it
should complain that the number is greater than 8.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 hw/arm/virt.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 4e7160ce96997..8ec346f8fda3e 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -923,7 +923,7 @@ static void machvirt_init(MachineState *machine)
     qemu_irq pic[NUM_IRQS];
     MemoryRegion *sysmem = get_system_memory();
     int gic_version = vms->gic_version;
-    int n;
+    int n, max_cpus;
     MemoryRegion *ram = g_new(MemoryRegion, 1);
     const char *cpu_model = machine->cpu_model;
     VirtBoardInfo *vbi;
@@ -957,6 +957,22 @@ static void machvirt_init(MachineState *machine)
         exit(1);
     }
 
+    /* The maximum number of CPUs depends on the GIC version, or on how
+     * many redistributors we can fit into the memory map.
+     */
+    if (gic_version == 3) {
+        max_cpus = vbi->memmap[VIRT_GIC_REDIST].size / 0x20000;
+    } else {
+        max_cpus = GIC_NCPU;
+    }
+
+    if (smp_cpus > max_cpus) {
+        error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
+                     "supported by machine 'mach-virt' (%d)",
+                     smp_cpus, max_cpus);
+        exit(1);
+    }
+
     vbi->smp_cpus = smp_cpus;
 
     if (machine->ram_size > vbi->memmap[VIRT_MEM].size) {
@@ -1155,10 +1171,11 @@ static void virt_class_init(ObjectClass *oc, void *data)
 
     mc->desc = "ARM Virtual Machine",
     mc->init = machvirt_init;
-    /* Our maximum number of CPUs depends on how many redistributors
-     * we can fit into memory map
+    /* Start max_cpus at the maximum QEMU supports. We'll further restrict
+     * it later in machvirt_init, where we have more information about the
+     * configuration of the particular instance.
      */
-    mc->max_cpus = a15memmap[VIRT_GIC_REDIST].size / 0x20000;
+    mc->max_cpus = MAX_CPUMASK_BITS;
     mc->has_dynamic_sysbus = true;
     mc->block_default_type = IF_VIRTIO;
     mc->no_cdrom = 1;
-- 
2.4.3