Re: [Qemu-devel] WfW setup and DOS display.sys hanging

[Gerd Hoffmann <kraxel@redhat.com>]

[ adding seabios list ]

On Di, 2014-02-04 at 20:47 +0100, Kevin Wolf wrote:
> Hi Gerd,
> 
> Am 09.01.2014 um 00:20 hat Sebastian geschrieben:
> > Hi,
> > 
> > I noticed in newer versions of Qemu (Debian Jessie) a regression
> > causing DISPLAY.SYS from MS-DOS 6.22 to hang the system as soon as
> > loaded.
> 
> now that you sent a pull request for a SeaBIOS update, I tried what
> would happen with this one. Sadly, while it does fix my hanging Win 7
> boot, DOS still hangs while loading display.sys.

[ This is http://www.kraxel.org/cgit/qemu/tag/?id=pull-roms-1
  with the 1.7.4 update ]

Digged out my prehistoric msdos floppy images.  Can confirm the hang.
Using default vga (i.e. cirrus).

Switching back to lgplvgabios ("make -C roms lgplvgabios" in qemu src
tree) makes the hang go away.

> Any ideas where to look, or are you going to have a look yourself? When
> I tried to debug it a while ago, I didn't see anything obvious, but then
> I didn't invest that much time for it either.

"perf kvm stat live" shows tons of NMIs:

             VM-EXIT    Samples  Samples%     Time%   Min Time   Max Time         Avg time 

       EXCEPTION_NMI     660538    99.82%    99.40%        0us      183us      0.67us ( +-   0.14% )
  EXTERNAL_INTERRUPT       1133     0.17%     0.58%        0us       43us      2.25us ( +-   4.86% )
      IO_INSTRUCTION         18     0.00%     0.01%        1us        5us      3.39us ( +-   6.50% )
   PENDING_INTERRUPT         17     0.00%     0.01%        1us       11us      2.15us ( +-  26.24% )

How can one get a trace log of all the kvm tracepoints these days?

'perf list' shows a bunch of kvm trace events,
but "perf trace -e '*kvm*' doesn't show me anything ...

cheers,
  Gerd

> I haven't tried out any of the other cases described below.

[ keeping full quote for seabios list ]

> > 
> > The Windows for Workgroups 3.11 SETUP.EXE file hangs with a cleared
> > screen and the cursor blinking in the top left of the screen. The
> > DOSIDLE.EXE[1] file hangs after printing out some system
> > information.
> > 
> > Git-Bisecting returned "roms: update vgabios binaries" (commit
> > 6eefccc0bb9c34051b1e21880fc3a1c1c8686edd) as the bad commit.
> > 
> > I tested the i386-softmmu target on Debian 7.3 (wheezy), x86_64 host
> > and gcc 4.7.2 (Debian 4.7.2-5) without KVM support.
> > 
> > [1] Source and binary are available e.g. at
> > http://maribu.home.xs4all.nl/zeurkous/download/mirror/dosidle/
> > 
> > Best Regards,
> > Sebastian