A little off topic thing: isn't the default resolution supposed to be
1024x768? This is the Microsoft regulation which all my physical devices
seem to follow:

https://docs.microsoft.com/en-us/windows-hardware/test/hlk/testref/6afc8979-df62-4d86-8f6a-99f05bbdc7f3

And when the user provides an EDID one should parse it and set the default
resolution to match it. But that's a less important feature.


On Tue, Apr 21, 2020 at 9:03 PM Laszlo Ersek <lersek@redhat.com> wrote:

> On 04/20/20 16:13, Gerd Hoffmann wrote:
> >   Hi,
> >
> >> So I would say that the symptom you see is a QEMU v4.1.0 regression.
> >> The QemuRamfbGraphicsOutputSetMode() function in the OVMF ramfb
> >> driver certainly needs the QemuFwCfgWriteBytes() call to work, for
> >> changing the resolution.
> >
> > Oh?  QemuRamfbGraphicsOutputSetMode() can be called multiple times?
> > How does that happen?
>
> QemuRamfbGraphicsOutputSetMode() is the "SetMode" member function of the
> EFI_GRAPHICS_OUTPUT_PROTOCOL instance that QemuRamfbDxe produces.
>
> This is a standard protocol; UEFI drivers and applications are free to
> locate it and to use it.
>
> (1) When you launch OVMF, you get the splash screen in a particular
> resolution. This resolution:
> - is configured by OvmfPkg/PlatformDxe,
> - is inherited by an OS boot loader,
> - is reconfigurable with OvmfPkg/PlatformDxe, for the next boot, via the
>   Setup TUI,
> - defaults to 800x600 (taking effect when no particular choice is
>   configured).
>
> (2) UiApp -- the Setup TUI itself -- uses its own resolution. Under
> OVMF, this resolution is fixed 640x480. When UiApp is entered,
> ultimately a call is made to QemuRamfbGraphicsOutputSetMode() -- i.e., a
> GOP.SetMode() member function -- for setting this 640x480 resolution.
>
> Using the following command:
>
>   qemu-system-x86_64 \
>     -nodefaults \
>     -boot menu=on,splash-time=5000 \
>     -enable-kvm \
>     -device ramfb \
>     -drive
> if=pflash,readonly,format=raw,file=$PREFIX/share/qemu/edk2-x86_64-code.fd \
>     -drive
> if=pflash,snapshot,format=raw,file=$PREFIX/share/qemu/edk2-i386-vars.fd \
>     -debugcon file:ovmf.log \
>     -global isa-debugcon.iobase=0x402
>
> when you first see the progress bar, the graphical resolution (1) is
> 800x600. Accordingly, QEMU prints to stderr:
>
> > ramfb_fw_cfg_write: 800x600 @ 0x6702000
>
> Once you hit ESC to interrupt the progress bar and to enter the Setup
> TUI, UiApp switches to resolution (2), 640x480. QEMU prints:
>
> > ramfb_fw_cfg_write: 640x480 @ 0x6702000
> > ramfb_fw_cfg_write: resolution locked, change rejected
>
> And you get garbage in the Setup window.
>
> Thanks,
> Laszlo
>
>