KVM entry failed, hardware error

[Johannes Bauer <dfnsonfsduifb@gmx.de>]

Hi list,

when trying to install Windows7 in a qemu-kvm 1.0.1 installation on
Gentoo on my host running

Linux joequad 3.3.7 #1 SMP PREEMPT Sun Jun 3 12:05:59 CEST 2012 x86_64
Intel(R) Core(TM)2 Quad CPU Q9550 @ 2.83GHz GenuineIntel GNU/Linux

with a host CPU of

processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 23
model name	: Intel(R) Core(TM)2 Quad CPU    Q9550  @ 2.83GHz
stepping	: 10
microcode	: 0xa07
cpu MHz		: 2003.000
cache size	: 6144 KB
physical id	: 0
siblings	: 4
core id		: 0
cpu cores	: 4
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm
constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64
monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm
dts tpr_shadow vnmi flexpriority
bogomips	: 5680.90
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management:

the installation first works fine but upon first reboot qemu terminates
with:

KVM: entry failed, hardware error 0x80000021

If you're runnning a guest on an Intel machine without unrestricted mode
support, the failure can be most likely due to the guest entering an invalid
state for Intel VT. For example, the guest maybe running in big real mode
which is not supported on less recent Intel processors.

EAX=00000010 EBX=00000080 ECX=00000000 EDX=00000080
ESI=0025da4a EDI=0007da4a EBP=00001f20 ESP=00000200
EIP=0000009b EFL=00000002 [-------] CPL=3 II=0 A20=1 SMM=0 HLT=0
ES =0020 00000200 0000ffff 00009300
CS =b000 002b0000 0000ffff 0000f300
SS =0020 00000200 0000ffff 0000f300
DS =0020 00000200 0000ffff 00009300
FS =0020 00000200 0000ffff 00009300
GS =0020 00000200 0000ffff 00009300
LDT=0000 00000000 0000ffff 00008200
TR =0000 00000000 0000ffff 00008b00
GDT=     002b0000 00000027
IDT=     00000000 000003ff
CR0=00000010 CR2=00000000 CR3=00000000 CR4=00000000
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000
DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
EFER=0000000000000000
Code=02 00 00 ea 91 00 00 00 18 00 0f 20 c0 66 83 e0 fe 0f 22 c0 <66> 31
c0 8e d8 8e c0 8e d0 66 bc 00 04 00 00 8e e0 8e e8 ea 00 00 00 20 00 00
00 20 4a da

which disassembles to

   0:   02 00                   add    (%eax),%al
   2:   00 ea                   add    %ch,%dl
   4:   91                      xchg   %eax,%ecx
   5:   00 00                   add    %al,(%eax)
   7:   00 18                   add    %bl,(%eax)
   9:   00 0f                   add    %cl,(%edi)
   b:   20 c0                   and    %al,%al
   d:   66 83 e0 fe             and    $0xfffffffe,%ax
  11:   0f 22 c0                mov    %eax,%cr0
  14:   66 31 c0                xor    %eax,%eax
  17:   8e d8                   mov    %ax,%ds
  19:   8e c0                   mov    %ax,%es
  1b:   8e d0                   mov    %ax,%ss
  1d:   66 bc 00 04 00 00       mov    $0x400,%esp
  23:   8e e0                   mov    %ax,%fs
  25:   8e e8                   mov    %ax,%gs
  27:   ea 00 00 00 20          ljmp   $0x2000,$0x0

Since the instruction clears PE of %cr0, I'm pretty sure it's trying to
enter real mode again (for a very brief period no doubt) before firing
up the OS. Since I believe my CPU is too old and does not support
"Unrestricted Guest", this causes qemu to barf.

Is this assessment correct? Is there some way of getting qemu to switch
to "soft" emulation in real mode and to use KVM in protected mode? Or is
it impossible to run Windows 7 with kvm on a Core Quad (which possibly
doesn't support "Unrestricted Guest")?

For reference, there's at least one more person having an identical
problem (I've also posted in that thread):
http://forums.gentoo.org/viewtopic-p-7054198.html

To find out if my CPU really does not suport "Unrestricted Guest" I've
also posted http://software.intel.com/en-us/forums/showthread.php?t=105687

Any help is greatly appreciated,
Best regards,
Joe