[PATCH v2 11/11] softmmu/vl: Exit gracefully when accelerator is not supported

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

Before configuring an accelerator, check it is valid for
the current machine. Doing so we can return a simple error
message instead of criptic one.

Before:

  $ qemu-system-arm -M raspi2b -enable-kvm
  qemu-system-arm: /build/qemu-ETIdrs/qemu-4.2/exec.c:865: 
cpu_address_space_init: Assertion `asidx == 0 || !kvm_enabled()' failed.
  Aborted

  $ qemu-system-aarch64 -M xlnx-zcu102 -enable-kvm -smp 6
  qemu-system-aarch64: kvm_init_vcpu: kvm_arch_init_vcpu failed (0): Invalid 
argument

After:

  $ qemu-system-arm -M raspi2b -enable-kvm
  qemu-system-aarch64: invalid accelerator 'kvm' for machine raspi2b

  $ qemu-system-aarch64 -M xlnx-zcu102 -enable-kvm -smp 6
  qemu-system-aarch64: -accel kvm: invalid accelerator 'kvm' for machine 
xlnx-zcu102

Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
---
 softmmu/vl.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/softmmu/vl.c b/softmmu/vl.c
index b219ce1f357..f2c4074310b 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2133,6 +2133,7 @@ static int do_configure_accelerator(void *opaque, 
QemuOpts *opts, Error **errp)
     const char *acc = qemu_opt_get(opts, "accel");
     AccelClass *ac = accel_find(acc);
     AccelState *accel;
+    MachineClass *mc;
     int ret;
     bool qtest_with_kvm;
 
@@ -2145,6 +2146,12 @@ static int do_configure_accelerator(void *opaque, 
QemuOpts *opts, Error **errp)
         }
         return 0;
     }
+    mc = MACHINE_GET_CLASS(current_machine);
+    if (!qtest_chrdev && !machine_class_valid_for_accelerator(mc, ac->name)) {
+        *p_init_failed = true;
+        error_report("invalid accelerator '%s' for machine %s", acc, mc->name);
+        return 0;
+    }
     accel = ACCEL(object_new_with_class(OBJECT_CLASS(ac)));
     object_apply_compat_props(OBJECT(accel));
     qemu_opt_foreach(opts, accelerator_set_property,
-- 
2.26.2