Hyper-V Synthetic Video Frame Buffer Driver may distort top two lines of console

Hyper-V Synthetic Video Frame Buffer Driver may distort top two lines of console

[Brian Wong]

I've identified another possible bug in the Hyper-V drivers: When the 
Hyper-V Synthetic Video Frame Buffer Driver is built into the kernel, 
and the VM is paused and continued, the top two lines of the console may 
become distorted. See the image at http://imgur.com/kIExFP3.

Can someone look into it?
-- 
Brian Wong
http://www.fierydragonlord.com

Re: Hyper-V Synthetic Video Frame Buffer Driver may distort top two lines of console

[Brian Wong]

On 3/6/2014 3:41 PM, Brian Wong wrote:
> I've identified another possible bug in the Hyper-V drivers: When the
> Hyper-V Synthetic Video Frame Buffer Driver is built into the kernel,
> and the VM is paused and continued, the top two lines of the console may
> become distorted. See the image at http://imgur.com/kIExFP3.
>
> Can someone look into it?

Just to clarify, I can confirm this bug under both the patched Gentoo 
3.10.32 kernel and the vanilla 3.13.5 kernel (see the image at 
http://imgur.com/mYUTzgt). Is the framebuffer somehow getting corrupted?

-- 
Brian Wong
http://www.fierydragonlord.com

Re: Hyper-V Synthetic Video Frame Buffer Driver may distort top two lines of console

[Brian Wong]

On 3/6/2014 4:05 PM, Brian Wong wrote:
> On 3/6/2014 3:41 PM, Brian Wong wrote:
>> I've identified another possible bug in the Hyper-V drivers: When the
>> Hyper-V Synthetic Video Frame Buffer Driver is built into the kernel,
>> and the VM is paused and continued, the top two lines of the console may
>> become distorted. See the image at http://imgur.com/kIExFP3.
>>
>> Can someone look into it?
>
> Just to clarify, I can confirm this bug under both the patched Gentoo
> 3.10.32 kernel and the vanilla 3.13.5 kernel (see the image at
> http://imgur.com/mYUTzgt). Is the framebuffer somehow getting corrupted?
>

The problem also reproduces under Kali Linux with kernel 3.12.6, but 
only on virtual consoles that are not hosting a graphical X session. The 
problem does not appear in X.

-- 
Brian Wong
http://www.fierydragonlord.com

RE: Hyper-V Synthetic Video Frame Buffer Driver may distort top two lines of console

[KY Srinivasan]

> -----Original Message-----
> From: Brian Wong [mailto:draconicpenguin1@yahoo.com]
> Sent: Friday, March 7, 2014 3:19 AM
> To: KY Srinivasan; linux-kernel@vger.kernel.org
> Subject: Re: Hyper-V Synthetic Video Frame Buffer Driver may distort top
> two lines of console
> 
> On 3/6/2014 4:05 PM, Brian Wong wrote:
> > On 3/6/2014 3:41 PM, Brian Wong wrote:
> >> I've identified another possible bug in the Hyper-V drivers: When the
> >> Hyper-V Synthetic Video Frame Buffer Driver is built into the kernel,
> >> and the VM is paused and continued, the top two lines of the console
> >> may become distorted. See the image at http://imgur.com/kIExFP3.
> >>
> >> Can someone look into it?
Haiyang (copied here) will look into it.

Regards,

K. Y
> >
> > Just to clarify, I can confirm this bug under both the patched Gentoo
> > 3.10.32 kernel and the vanilla 3.13.5 kernel (see the image at
> > http://imgur.com/mYUTzgt). Is the framebuffer somehow getting
> corrupted?
> >
> 
> The problem also reproduces under Kali Linux with kernel 3.12.6, but only on
> virtual consoles that are not hosting a graphical X session. The problem does
> not appear in X.
> 
> --
> Brian Wong
> http://www.fierydragonlord.com

RE: Hyper-V Synthetic Video Frame Buffer Driver may distort top two lines of console

[Haiyang Zhang]

> -----Original Message-----
> From: KY Srinivasan
> Sent: Thursday, March 6, 2014 4:51 PM
> To: Brian Wong; linux-kernel@vger.kernel.org; Haiyang Zhang
> Subject: RE: Hyper-V Synthetic Video Frame Buffer Driver may distort top
> two lines of console
> 
> 
> 
> > -----Original Message-----
> > From: Brian Wong [mailto:draconicpenguin1@yahoo.com]
> > Sent: Friday, March 7, 2014 3:19 AM
> > To: KY Srinivasan; linux-kernel@vger.kernel.org
> > Subject: Re: Hyper-V Synthetic Video Frame Buffer Driver may distort
> > top two lines of console
> >
> > On 3/6/2014 4:05 PM, Brian Wong wrote:
> > > On 3/6/2014 3:41 PM, Brian Wong wrote:
> > >> I've identified another possible bug in the Hyper-V drivers: When
> > >> the Hyper-V Synthetic Video Frame Buffer Driver is built into the
> > >> kernel, and the VM is paused and continued, the top two lines of
> > >> the console may become distorted. See the image at
> http://imgur.com/kIExFP3.
> > >>
> > >> Can someone look into it?
> Haiyang (copied here) will look into it.
> 

It's a known issue. The root cause is not very clear yet.
It doesn't affect system functions. But we will look into it 
further.

Thanks,
- Haiyang