hw/arm/virt: Make host as default CPU type on AArch64

Currently mach-virt machine model uses cortex-a15 as default CPU when -cpu option is missing. This caused confusion to certain virt tools (e.g. libvirt, virt-install) which don't suppply -cpu option while invoking qemu-kvm. To solve this problem this patch changes the default CPU type to "host" when target is AArch64.

NOTE: It doesn't use "cortex-a57" as default CPU type because cortex-a57 doesn't work on some 64bit ARM machine, such as APM Mustang. "host" is a safe bet for all AArch64 machines.

---
 hw/arm/virt.c | 4 ++++
 1 file changed, 4 insertions(+)

index 9072bc2..1e8371c 100644
@@ -731,7 +731,11 @@ static void machvirt_init(MachineState *machine)
     char **cpustr;
 
     if (!cpu_model) {
+#if defined(TARGET_AARCH64)
+        cpu_model = "host";
+#else
         cpu_model = "cortex-a15";
+#endif
     }
 
     /* Separate the actual CPU model name from any appended features */

1.8.3.1

This won't work if you're not using KVM, since 'host' isn't a valid CPU type there, and it will break working command lines as well. Also it breaks the current invariant of "command lines on qemu-system-arm also work on qemu-system-aarch64". I don't like the place we've ended up with the command line setup for the 64-bit virt board, but I don't think this is the correct fix...

-- PMM