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

[Vineeth Pillai]

On 6/4/2021 9:00 AM, Wei Liu wrote:
> 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.
I have just tried reverting the commit mentioned above and it solves the 
GUI freeze
I was also seeing. Previously, login screen was just freezing, but VM 
was accessible
through ssh. With the above commit reverted, I can login to Gnome.

Looks like I am also experiencing the same bug mentioned here.

Thanks,
Vineeth