Qemu Win98 VM with KVM videocard passthrough DOS mode video is not working for most of games..

This bug has been copied automatically from: https://bugs.launchpad.net/qemu/+bug/1873341
Reported by 'ruthan' on 2020-04-16 :

Hello,
im using Win98 machine with KVM videocards passthrough which is working
fine, but when i try Windows 98 - Dosbox mode, there is something work
with all videocards which i tried PCI-E/PCI - Nvidia, 3Dfx, Matrox.

 Often is framerate is very slow, as slideshow:
Doom 2,Battle Arena Toshidden 1 demo, Blood, even for Fdisk start - i can
see how its slowly rendering individual lines, or its not working at all -
freeze / black screen only - Warcraft 2 demo (vesa 640x480).

 There is something wrong with it. I can add more games info if is needed,
most of games which i tried are not working.

 Qemu 2.11 + 4.2, Linux Mint 19.3. Gigabyte Z170 MB.