For Windows Display Driver Model (WDDM) v2, Windows will renegotiate the size of a GPU BAR post firmware initialization on GPUs supporting resizable BAR, see Resizable BAR Capability in the
PCI SIG Specifications Library.
A GPU, supporting resizable BAR, must ensure that it can keep the display up and showing a static image during the reprogramming of the BAR. In particular, we don't want to see the display go blank and back up during this process. It is important to have smooth transition between the firmware displayed image, the boot loader image and the first kernel mode driver generated image. It is guaranteed that no PCI transaction will occur toward the GPU while the renegotiation is taking place.0