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

["Gonglei (Arei)" <arei.gonglei@xxxxxxxxxx>]

> -----Original Message-----
> From: Andreas FÃrber [mailto:afaerber@xxxxxxx]
> Sent: Friday, July 26, 2013 6:28 PM
> To: Gerd Hoffmann; Gonglei (Arei)
> Cc: Anthony Liguori; Hanweidong; Luonengjun; qemu-devel@xxxxxxxxxx;
> Huangweidong (Hardware); xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Qemu-devel] Cirrus VGA slow screen update, show blank screen
> last 13s or so for windows XP guest
> 
> Am 26.07.2013 12:19, schrieb Gerd Hoffmann:
> > On 07/26/13 12:02, Andreas FÃrber wrote:
> >> Am 26.07.2013 08:41, schrieb Gonglei (Arei):
> >>>> -----Original Message-----
> >>>> From: Anthony Liguori [mailto:anthony@xxxxxxxxxxxxx]
> >>>> Sent: Friday, July 26, 2013 11:21 AM
> >>>> To: Gonglei (Arei)
> >>>> Cc: qemu-devel@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxx; Hanweidong;
> >>>> Luonengjun; Huangweidong (Hardware)
> >>>> Subject: Re: [Qemu-devel] Cirrus VGA slow screen update, show blank
> screen
> >>>> last 13s or so for windows XP guest
> >>>>
> >>>>  On Thu, Jul 25, 2013 at 10:08 PM, Gonglei (Arei)
> >>>> <arei.gonglei@xxxxxxxxxx> wrote:
> >>>>> 3. Why does the traditional qemu has no blank screen problem on cirrus
> VGA
> >>>> emulation ?
> >>>>
> >>>> This is one of the few cases where TCG is actually faster than KVM or
> >>>> Xen.  In TCG, an MMIO exit is converted to a function call.  OTOH,
> >>>> even with KVM, an MMIO exit is at least a couples thousand cycles.
> >>>> It's worse with Xen because dom0 has to be scheduled.
> >>>
> >>> Perhaps I did not express clearly what I mean at #3.
> >>> I don't understand why the qemu-dm(qemu-0.10.2) works well
> >>> but the upstream qemu(begin with qemu-0.14) is not for the
> >>> same windows XP guest image in cirrus vga emulation. Does
> >>> the cirrus vga emulation have some differences between
> >>> qemu-dm and unstream qemu ?
> >>
> >> I don't know about qemu-dm, but QEMU switched from a home-grown pixel
> >> handling to pixman library sometime around 1.4. CC'ing Gerd.
> >
> > 0.14 != 1.4 ;)
> 
> Oops! In that case, Gonglei, try to reproduce the issue with upstream
> 0.10 and use git-bisect to find out when things got slower between
> v0.10.2..v0.14.0. It would be unrealistic to expect us to remember all
> Cirrus-related changes from 2-4 years ago. ;)

On KVM:
I reproduced the issues that the VNC client show blank screen when Windows XP 
guest booting up 
from qemu-kvm-0.11.0 to latest qemu-1.5.1. I wanted to test qemu-kvm-0.10, but 
I didn't 
know the right command on it. The command beginning with qemu-kvm-0.11.0 is:
./qemu-system-x86_64 -name winXP -m 2048 -smp 2 -drive 
file=/mnt/sdd/image/winxp_sp3_32_2U_cn -vnc 0.0.0.0:2 -vga cirrus

Hoping to help, thanks!

-Gonglei

> 
> Andreas
> 
> --
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 NÃrnberg, Germany
> GF: Jeff Hawn, Jennifer Guild, Felix ImendÃrffer; HRB 16746 AG NÃrnberg
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