hw/i386: Add the ramfb romfile compatibility

ramfb is a sysbus device so it can only used for machine types where it
is explicitly enabled:

  # git grep machine_class_allow_dynamic_sysbus_dev.*TYPE_RAMFB_DEVICE
  hw/arm/virt.c:    machine_class_allow_dynamic_sysbus_dev(mc,
		  TYPE_RAMFB_DEVICE);
  hw/i386/microvm.c:    machine_class_allow_dynamic_sysbus_dev(mc,
		  TYPE_RAMFB_DEVICE);
  hw/i386/pc_piix.c:    machine_class_allow_dynamic_sysbus_dev(m,
		  TYPE_RAMFB_DEVICE);
  hw/i386/pc_q35.c:    machine_class_allow_dynamic_sysbus_dev(m,
		  TYPE_RAMFB_DEVICE);
  hw/loongarch/virt.c:    machine_class_allow_dynamic_sysbus_dev(mc,
		  TYPE_RAMFB_DEVICE);
  hw/riscv/virt.c:    machine_class_allow_dynamic_sysbus_dev(mc,
		  TYPE_RAMFB_DEVICE);

So these six are the only machine types we have to worry about.

The three x86 machine types (pc, q35, microvm) will actually use the rom
(when booting with seabios).

For arm/riscv/loongarch virt we want to disable the rom.

This patch sets ramfb romfile option to false by default, except for x86
machines types (pc, q35, microvm) which need the rom file when booting
with seabios and machine types <= 10.0 (handling the case of arm virt,
for compat reasons).

At the same time, set the "use-legacy-x86-rom" property to true on those
historical versioned machine types in order to avoid the memory layout
being changed.

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Shaoqin Huang <shahuang@redhat.com>
Message-ID: <20250717100941.2230408-4-shahuang@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

6 files changed, 20 insertions, 2 deletions

diff --git a/hw/core/machine.c b/hw/core/machine.c
index e869821..a7043e2 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -39,6 +39,8 @@
 
 GlobalProperty hw_compat_10_0[] = {
     { "scsi-hd", "dpofua", "off" },
+    { "ramfb", "use-legacy-x86-rom", "true"},
+    { "vfio-pci", "use-legacy-x86-rom", "true" },
 };
 const size_t hw_compat_10_0_len = G_N_ELEMENTS(hw_compat_10_0);
 
diff --git a/hw/display/ramfb-standalone.c b/hw/display/ramfb-standalone.c
index 82d8c69..72b2071 100644
--- a/hw/display/ramfb-standalone.c
+++ b/hw/display/ramfb-standalone.c
@@ -64,7 +64,7 @@ static const VMStateDescription ramfb_dev_vmstate = {
 static const Property ramfb_properties[] = {
     DEFINE_PROP_BOOL("x-migrate", RAMFBStandaloneState, migrate,  true),
     DEFINE_PROP_BOOL("use-legacy-x86-rom", RAMFBStandaloneState,
-                     use_legacy_x86_rom, true),
+                     use_legacy_x86_rom, false),
 };
 
 static void ramfb_class_initfn(ObjectClass *klass, const void *data)
diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
index e0daf0d..d90b69a 100644
--- a/hw/i386/microvm.c
+++ b/hw/i386/microvm.c
@@ -49,6 +49,7 @@
 #include "hw/acpi/generic_event_device.h"
 #include "hw/pci-host/gpex.h"
 #include "hw/usb/xhci.h"
+#include "hw/vfio/types.h"
 
 #include "elf.h"
 #include "kvm/kvm_i386.h"
@@ -633,6 +634,8 @@ GlobalProperty microvm_properties[] = {
      * so reserving io space is not going to work.  Turn it off.
      */
     { "pcie-root-port", "io-reserve", "0" },
+    { TYPE_RAMFB_DEVICE, "use-legacy-x86-rom", "true" },
+    { TYPE_VFIO_PCI, "use-legacy-x86-rom", "true" },
 };
 
 static void microvm_class_init(ObjectClass *oc, const void *data)
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index a3285fb..ad5caff 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -49,6 +49,7 @@
 #include "hw/i2c/smbus_eeprom.h"
 #include "system/memory.h"
 #include "hw/acpi/acpi.h"
+#include "hw/vfio/types.h"
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "system/xen.h"
@@ -77,6 +78,13 @@ static const int ide_iobase2[MAX_IDE_BUS] = { 0x3f6, 0x376 };
 static const int ide_irq[MAX_IDE_BUS] = { 14, 15 };
 #endif
 
+static GlobalProperty pc_piix_compat_defaults[] = {
+    { TYPE_RAMFB_DEVICE, "use-legacy-x86-rom", "true" },
+    { TYPE_VFIO_PCI, "use-legacy-x86-rom", "true" },
+};
+static const size_t pc_piix_compat_defaults_len =
+    G_N_ELEMENTS(pc_piix_compat_defaults);
+
 /*
  * Return the global irq number corresponding to a given device irq
  * pin. We could also use the bus number to have a more precise mapping.
@@ -492,6 +500,8 @@ static void pc_i440fx_machine_options(MachineClass *m)
                                    pc_set_south_bridge);
     object_class_property_set_description(oc, "x-south-bridge",
                                      "Use a different south bridge than PIIX3");
+    compat_props_add(m->compat_props,
+                     pc_piix_compat_defaults, pc_piix_compat_defaults_len);
 }
 
 static void pc_i440fx_machine_10_1_options(MachineClass *m)
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index cf871cf..9b9519f 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -45,6 +45,7 @@
 #include "hw/i386/pc.h"
 #include "hw/i386/amd_iommu.h"
 #include "hw/i386/intel_iommu.h"
+#include "hw/vfio/types.h"
 #include "hw/virtio/virtio-iommu.h"
 #include "hw/display/ramfb.h"
 #include "hw/ide/pci.h"
@@ -67,6 +68,8 @@
 
 static GlobalProperty pc_q35_compat_defaults[] = {
     { TYPE_VIRTIO_IOMMU_PCI, "aw-bits", "39" },
+    { TYPE_RAMFB_DEVICE, "use-legacy-x86-rom", "true" },
+    { TYPE_VFIO_PCI, "use-legacy-x86-rom", "true" },
 };
 static const size_t pc_q35_compat_defaults_len =
     G_N_ELEMENTS(pc_q35_compat_defaults);
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 0b969b3..174499e 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -3810,7 +3810,7 @@ static const TypeInfo vfio_pci_dev_info = {
 static const Property vfio_pci_dev_nohotplug_properties[] = {
     DEFINE_PROP_BOOL("ramfb", VFIOPCIDevice, enable_ramfb, false),
     DEFINE_PROP_BOOL("use-legacy-x86-rom", VFIOPCIDevice,
-                     use_legacy_x86_rom, true),
+                     use_legacy_x86_rom, false),
     DEFINE_PROP_ON_OFF_AUTO("x-ramfb-migrate", VFIOPCIDevice, ramfb_migrate,
                             ON_OFF_AUTO_AUTO),
 };