Hi All,
With QEMU 7.0.0 and SeaBIOS 1.16.0, virtual machines with a PCIe
graphics card connected to a PCIe Root Port, rather than the Root
Complex, as recommended by the QEMU PCI Express Guidelines[1], are
unable to use VESA BIOS Extensions display modes. For example,
qemu-system-x86_64 \
-no-user-config \
-nodefaults \
-machine q35,accel=kvm \
-m 1G \
-cdrom "$iso" \
-device VGA
works well and can use many VBE display modes, while
qemu-system-x86_64 \
-no-user-config \
-nodefaults \
-machine q35,accel=kvm \
-m 1G \
-cdrom "$iso" \
-device pcie-root-port,id=pci.1,bus=pcie.0 \
-device VGA,bus=pci.1
only shows a few text display modes. This is the case for VGA,
qxl-vga, and virtio-vga devices. `info qtree` shows the device as
`type: PCIE` in both configurations. High-resolution graphics modes
are available when using UEFI (OVMF) in both configurations.
Am I correct in assuming this is a limitation of SeaVGABIOS? Is this
expected behavior, or a bug? If it's unlikely to change soon, would
it make sense for me to propose documenting this limitation in the
QEMU PCI Express Guidelines?
I'd appreciate any insights you might have.
Thanks,
Kevin
[1]: https://github.com/qemu/qemu/blob/v7.0.0/docs/pcie.txt
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