Am Tue, 18 Feb 2020 18:37:09 +0100
schrieb Paolo Bonzini <pbonzini@redhat.com>:

> On 18/02/20 18:27, Olaf Hering wrote:
> > The approach below (making 'xenfv' an alias of 'pc') does not work:
> > xen_enabled() is false when pc_i440fx_3_1_machine_options runs.  
> Don't use an alias, copy the 3.1 code into the xenfv machine type and/or
> call the 3.1 functions from the xenfv machine type.

Since pci_create_simple must be called after pc_init1, the change appears to be as simple as this:

@@ -949,6 +953,7 @@ DEFINE_PC_MACHINE(isapc, "isapc", pc_init_isa,
 #ifdef CONFIG_XEN
 static void xenfv_machine_options(MachineClass *m)
 {
+    pc_i440fx_3_1_machine_options(m);
     m->desc = "Xen Fully-virtualized PC";
     m->max_cpus = HVM_MAX_VCPUS;
     m->default_machine_opts = "accel=xen";

There will likely be an argument about making xenfv compatible with 3.1 or 4.2. I guess the only consensus will be configure option.

Olaf