Use virtio-gpu with viogpudo on Arm64 Windows 11

Replace ramfb with virtio-gpu-pci at 2048x1280 and install the viogpudo
driver from the VirtIO ISO. ramfb has a fixed mode, and keeping both
adapters left Windows with a second, fixed-mode monitor.

Windows Setup and the base image have no viogpudo driver, so on the
launch that creates the system disk the launcher also adds a ramfb ahead
of the config files. The display window shows the first GPU.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

qemu/windows11-darwin-arm64.ini

@@ -24,11 +24,15 @@
   driver = "virtio-net-pci"
   netdev = "net0"
 
-# Unlike q35, "virt" has no default GPU or keyboard. ramfb is used rather than
-# virtio-gpu because the firmware's virtio-gpu output freezes at the Windows
-# boot manager; Windows drives either one through its basic display driver.
+# Unlike q35, "virt" has no default GPU or keyboard. virtio-gpu is the only
+# display, driven by viogpudo (installed by Configure-Windows.ps1). ramfb is not
+# added because Windows would then see a second adapter with a fixed-mode
+# monitor. xres/yres set the preferred mode in the EDID (QEMU defaults to
+# 1280x800); viogpudo accepted 1920x1200 and 2048x1280 but not 2560x1600.
 [device "gpu0"]
-  driver = "ramfb"
+  driver = "virtio-gpu-pci"
+  xres = "2048"
+  yres = "1280"
 
 [device "kbd0"]
   driver = "usb-kbd"

qemu/windows11-linux-arm64.ini

@@ -24,11 +24,15 @@
   driver = "virtio-net-pci"
   netdev = "net0"
 
-# Unlike q35, "virt" has no default GPU or keyboard. ramfb is used rather than
-# virtio-gpu because the firmware's virtio-gpu output freezes at the Windows
-# boot manager; Windows drives either one through its basic display driver.
+# Unlike q35, "virt" has no default GPU or keyboard. virtio-gpu is the only
+# display, driven by viogpudo (installed by Configure-Windows.ps1). ramfb is not
+# added because Windows would then see a second adapter with a fixed-mode
+# monitor. xres/yres set the preferred mode in the EDID (QEMU defaults to
+# 1280x800); viogpudo accepted 1920x1200 and 2048x1280 but not 2560x1600.
 [device "gpu0"]
-  driver = "ramfb"
+  driver = "virtio-gpu-pci"
+  xres = "2048"
+  yres = "1280"
 
 [device "kbd0"]
   driver = "usb-kbd"

run-windows11.py

@@ -372,7 +372,12 @@ for label, host_port, guest_port in (("RDP", rdp_port, 3389), ("SSH", ssh_port,
     else:
         forwards.append(f"hostfwd=tcp::{host_port}-:{guest_port}")
 
-qemu_args = [
+# Neither Windows Setup nor the base image has the viogpudo driver yet, and
+# without it the virtio-gpu in the config file shows "display output is not
+# active". ramfb shows the screen until Configure-Windows.ps1 installs it. It
+# must be created before the virtio-gpu: the display window shows the first GPU.
+qemu_args = ["-device", "ramfb"] if installing and host_arch == "arm64" else []
+qemu_args += [
     "-readconfig", str(qemu_config),
     "-readconfig", str(qemu_platform_config),
     # "max" is the host CPU under KVM/HVF and the fullest model under TCG.

seediso/windows11/Configure-Windows.ps1

@@ -45,7 +45,8 @@ function Install-VirtIOArm64Drivers {
         @{ Folder = 'vioserial'; Inf = 'vioser.inf' },
         @{ Folder = 'Balloon'; Inf = 'balloon.inf' },
         @{ Folder = 'viorng'; Inf = 'viorng.inf' },
-        @{ Folder = 'vioinput'; Inf = 'vioinput.inf' }
+        @{ Folder = 'vioinput'; Inf = 'vioinput.inf' },
+        @{ Folder = 'viogpudo'; Inf = 'viogpudo.inf' }
     )
 
     $installed = 0