[bug report] Commit ccf953d8f3d6 ("fb_defio: Remove custom address_space_operations") breaks Hyper-V FB driver

[Vitaly Kuznetsov]

Hi,

Commit ccf953d8f3d6 ("fb_defio: Remove custom address_space_operations")
seems to be breaking Hyper-V framebuffer
(drivers/video/fbdev/hyperv_fb.c) driver for me: Hyper-V guest boots
well and plymouth even works but when I try starting Gnome, virtual
screen just goes black. Reverting the above mentioned commit on top of
5.13-rc4 saves the day. The behavior is 100% reproducible. I'm using
Gen2 guest runing on Hyper-V 2019. It was also reported that Gen1 guests
are equally broken.

Is this something known?

-- 
Vitaly