pseries: allow setting stdout-path even on machines with a VGA

-machine graphics=off is the usual way to tell the firmware or the OS that the
user wants a serial console.  The pseries machine however does not support
this, and never adds the stdout-path node to the device tree if a VGA device
is provided.  This is in addition to the other magic behavior of VGA devices,
which is to add a keyboard and mouse to the default USB bus.

Split spapr->has_graphics in two variables so that the two behaviors can be
separated: the USB devices remains the same, but the stdout-path is added
even with "-device VGA -machine graphics=off".

Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220507054826.124936-1-pbonzini@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

hw/ppc/spapr.c

@@ -1066,7 +1066,7 @@ static void spapr_dt_chosen(SpaprMachineState *spapr, void *fdt, bool reset)
             _FDT(fdt_setprop_string(fdt, chosen, "qemu,boot-device", boot_device));
         }
 
-        if (!spapr->has_graphics && stdout_path) {
+        if (spapr->want_stdout_path && stdout_path) {
             /*
              * "linux,stdout-path" and "stdout" properties are
              * deprecated by linux kernel. New platforms should only
@@ -2712,6 +2712,7 @@ static void spapr_machine_init(MachineState *machine)
     const char *kernel_filename = machine->kernel_filename;
     const char *initrd_filename = machine->initrd_filename;
     PCIHostState *phb;
+    bool has_vga;
     int i;
     MemoryRegion *sysmem = get_system_memory();
     long load_limit, fw_size;
@@ -2950,9 +2951,12 @@ static void spapr_machine_init(MachineState *machine)
     }
 
     /* Graphics */
-    if (spapr_vga_init(phb->bus, &error_fatal)) {
-        spapr->has_graphics = true;
+    has_vga = spapr_vga_init(phb->bus, &error_fatal);
+    if (has_vga) {
+        spapr->want_stdout_path = !machine->enable_graphics;
         machine->usb |= defaults_enabled() && !machine->usb_disabled;
+    } else {
+        spapr->want_stdout_path = true;
     }
 
     if (machine->usb) {
@@ -2962,7 +2966,7 @@ static void spapr_machine_init(MachineState *machine)
             pci_create_simple(phb->bus, -1, "nec-usb-xhci");
         }
 
-        if (spapr->has_graphics) {
+        if (has_vga) {
             USBBus *usb_bus = usb_bus_find(-1);
 
             usb_create_simple(usb_bus, "usb-kbd");

include/hw/ppc/spapr.h

@@ -194,7 +194,7 @@ struct SpaprMachineState {
     Vof *vof;
     uint64_t rtc_offset; /* Now used only during incoming migration */
     struct PPCTimebase tb;
-    bool has_graphics;
+    bool want_stdout_path;
     uint32_t vsmt;       /* Virtual SMT mode (KVM's "core stride") */
 
     /* Nested HV support (TCG only) */