[PATCH 6/9] hw/arm/virt: Display list of valid CPUs for the Virt machine

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

The Virt machine is restricted to a subset of the CPU provided
by QEMU. Instead of having the user run '--cpu help' and try
each CPUs until finding a match, display the list from start:

  $ qemu-system-aarch64 -M virt -cpu cortex-a8
  qemu-system-aarch64: mach-virt: CPU type cortex-a8 not supported
  qemu-system-aarch64: mach-virt: Please select one of the following CPU types:  cortex-a7, cortex-a15, cortex-a53, cortex-a57, cortex-a72, host, max

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 hw/arm/virt.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 7802d3a66e8..6ffe091804f 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1830,9 +1830,20 @@ static void machvirt_init(MachineState *machine)
 
     if (!cpu_type_valid(machine->cpu_type)) {
         int len = strlen(machine->cpu_type) - strlen(ARM_CPU_TYPE_SUFFIX);
+        g_autoptr(GString) s = g_string_new(NULL);
 
         error_report("mach-virt: CPU type %.*s not supported",
                      len, machine->cpu_type);
+
+        for (n = 0; n < ARRAY_SIZE(valid_cpus); n++) {
+            len = strlen(valid_cpus[n]) - strlen(ARM_CPU_TYPE_SUFFIX);
+            g_string_append_printf(s, " %.*s", len, valid_cpus[n]);
+            if (n + 1 < ARRAY_SIZE(valid_cpus)) {
+                g_string_append_c(s, ',');
+            }
+        }
+        error_report("mach-virt: Please select one of the following CPU types: %s",
+                     g_string_free(s, FALSE));
         exit(1);
     }
 
-- 
2.26.2