Regression: gvt: vgpu 1: MI_LOAD_REGISTER_MEM handler error

[Alex Williamson]

Running a Windows guest on a i915-GVTg_V4_2 from an HD 5500 IGD on
v5.12-rc6 results in host logs:

gvt: vgpu 1: lrm access to register (20c0)
gvt: vgpu 1: MI_LOAD_REGISTER_MEM handler error
gvt: vgpu 1: cmd parser error
0x0 
0x29 

gvt: vgpu 1: scan wa ctx error
gvt: vgpu 1: failed to submit desc 0
gvt: vgpu 1: fail submit workload on ring rcs0
gvt: vgpu 1: fail to emulate MMIO write 00002230 len 4

The guest goes into a boot loop triggering this error before reaching
the desktop and rebooting.  Guest using Intel driver 20.19.15.5171
dated 11/4/2020 (from driver file 15.40.5171).

This VM works well with the same guest and userspace software stack on
Fedora's kernel 5.11.11-200.fc33.x86_64.  Thanks,

Alex