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

[Wei Liu]

On Fri, Jun 04, 2021 at 02:25:01PM +0200, Vitaly Kuznetsov wrote:
> 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?
> 

I've heard a similar report from Vineeth but we didn't get to the bottom
of this.

Wei.

> -- 
> Vitaly
>