[SeaBIOS] WinXP 32 installation failure with new SeaBIOS in QEMU

Avi Kivity avi at redhat.com
Sun Aug 19 13:39:04 CEST 2012


On 08/19/2012 12:27 PM, Avi Kivity wrote:
> On 08/17/2012 08:53 AM, Gerd Hoffmann wrote:
>>   Hi,
>> 
>>> It might be instruction emulator bug in KVM.
>>> Attached is the trace.
>> 
>>             qemu-2047  [000] d..2   261.999076: kvm_entry: vcpu 0
>>             qemu-2047  [000] ...1   261.999077: kvm_emulate_insn:
>> f0000:6201:fb (real)
>>             qemu-2047  [000] d..2   261.999078: kvm_entry: vcpu 0
>> ##### CPU 3 buffer started ####
>>             qemu-2047  [003] ...1   411.367592: kvm_emulate_insn:
>> 20000:26c:cb (prot16)
>>             qemu-2047  [003] ...1   411.367593: kvm_inj_exception: #GP
>> (0x844)
>>             qemu-2047  [003] d..2   411.367594: kvm_entry: vcpu 0
>> 
>> This looks suspious.  vcpu migration issue?  Or just something missing
>> in the trace?
>> 
> 
> Looks like tracing with a too-small buffer size.  I generally trace using
> 
>   trace-cmd record -e kvm -b 100000
> 
> and with fingers crossed.
> 
> The RET FAR instruction failure (which trace-cmd report decodes) is
> probably not the original failure.

In fact it is, we mis-emulated stack operations when SS.B=0 but the
address size was 32-bits, and there are bits set in the top 16 bits of ESP.

Why ESP has bits set in the top 16 bits is another question.  Is seabios
polluting those bits?


-- 
error compiling committee.c: too many arguments to function



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