[Qemu-devel] A number of OSes do not work with kqemu

[Bakul Shah]

The three I am aware of are: openbsd, netbsd & plan9.  They
work fine with -no-kqemu flag.  This is under freebsd but
I believe the same thing happens under linux.

The easiest test case may be plan 9 it seems to dies very
early.  Download the plan9 .iso from one of
    http://www.tip9ug.jp/mirror/plan9.iso.bz2
    http://www.9grid.de/plan9/plan9.iso.bz2

Decompress, fire up qemu and boot from the .iso, giving qemu
some hard disk image.  It will ask whether you want to
install plan9 or boot plan9 from from the CD.  Choose the
latter.  It will die almost right away with an error message
like this:

user fault: addr=00000000 pc=00001020
addr not mapped (vpd=00000000)
pc not mapped (vpd=00000000)
panic: boot process died: sys: trap: fault read addr=0x0 pc=0x00001020

I captured a log with `log all' command to qemu monitor
console and compared the two cases (with and without kqemu).
There are differences in the CCS register like so:

@@ -6489,7 +6489,7 @@
 GDT=     00000000 0000ffff
 IDT=     00000000 0000ffff
 CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
-CCS=00000000 CCD=0000f000 CCO=LOGICB  
+CCS=00000044 CCD=0000f000 CCO=EFLAGS  
 ----------------
 IN: 
 0x000f08e0:  add    $0x4,%sp
@@ -7818,7 +7818,7 @@
 GDT=     00000000 0000ffff
 IDT=     00000000 0000ffff
 CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000
-CCS=00000014 CCD=00000400 CCO=EFLAGS  
+CCS=00000000 CCD=00000400 CCO=INCW    
 ----------------
 IN: 
 0x000f9a53:  mov    $0x9fc0,%ax

diff done after filtering out lines matching egrep pattern
"Servicing hardware|kqemu" from both log outputs.

This is about as far as I can get without delving into qemu
and I certainly do not want to reverse engineer kqemu!

-- bakul