Re: [Qemu-devel] [Xen-devel] Cirrus VGA slow screen update, show blank screen last 13s or so for windows XP guest

[Fabio Fantoni <fabio.fantoni@m2r.biz>]

Il 25/07/2013 16:21, Gonglei (Arei) ha scritto:
>
>> -----Original Message-----
>> From: Fabio Fantoni [mailto:fabio.fantoni@m2r.biz]
>> Sent: Thursday, July 25, 2013 9:55 PM
>> To: Gonglei (Arei)
>> Cc: qemu-devel@nongnu.org; xen-devel@lists.xen.org; Hanweidong;
>> Luonengjun; Huangweidong (Hardware)
>> Subject: Re: [Xen-devel] Cirrus VGA slow screen update, show blank screen last
>> 13s or so for windows XP guest
>>
>> Il 25/07/2013 15:13, Gonglei (Arei) ha scritto:
>>> Hi,
>>>     I found a problem: For windows XP guest booting by qemu upstream,
>>> using the RDP(Remote Desktop Protocol) and VNC protocol to connect the
>> windows XP guest
>>> which booting by Qemu upstream respectively. the VNC client will become
>> blank screen last
>>> 13 seconds or so on XEN platform, and last 2 seconds on KVM. And through
>> debugging,
>>> the cirrus VGA card does not produce dirty pages during the blank screen's
>> times.
>>>     When -vga is changed from cirrus to std the issue goes away and the
>> update proceeds at normal speed.
>>> In addition, when using the Qemu-dm replace Qemu upstream on XEN
>> platform,
>>> the cirrus VGA works good and the issue goes away also.
>>>
>>>     Today, lots of googling have seen the same behavior:
>>>
>>> https://github.com/joyent/smartos-live/issues/215
>>> http://lists.gnu.org/archive/html/qemu-devel/2011-06/msg02105.html
>>> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=574988
>>> etc...
>>>
>>>     But, I test the latest qemu-1.5.1, the problem exist firmly.
>>>
>>>     Any ideas? Thanks!
>>>
>>> Best Regards!
>>> -Gonglei
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@lists.xen.org
>>> http://lists.xen.org/xen-devel
>> I've seen the perfomance problem too with vnc when I started to try
>> upstream qemu. I already reported it on the end of 2011 but no solution yet.
>> I found spice as an alternative: qxl vga will not work on xen until SSE
>> support will be added on hvm domU, but spice is usable with stdvga and
>> performance is better that vnc. Combined with vdagent and usb
>> redirection it makes a perfect vkvm, and more.
>> Spice basic support in xl is already present and for more features I
>> posted some patches here but they are not included in upstream for now.
>> Cirrus vga drivers are also old and have limitations on both windows and
>> linux and they can add other problems, they are probably not good for
>> recent os/de.
> Thanks for responding. I don't understand why the Qemu-dm works well
> but the upstream qemu is not for the same windows XP guest image.
> Does the Cirrus vga emulation have some differences between qemu-dm
> and unstream qemu ?
>
> -Gonglei
I did test on cirrus vga a long time ago, last was on videoram settings 
patch.
Try to increase videoram setting to see if you see an increasing in 
performances and/or the problem persists.
On my tests the performance seem identical.
Probably the causes of video problems with upstream qemu are some 
hardcoding on xen (probably on hvmloader and fixed seabios tables).
I wasn't able to found exactly problem.