Re: kvm guest for 486 sx

[Jerry Geis <geisj@pagestation.com>]

Avi Kivity wrote:
> On 07/07/2009 03:36 PM, Jerry Geis wrote:
>>
>> Avi Kivity wrote:
>>> On 07/07/2009 03:06 PM, Jerry Geis wrote:
>>>>> Try -cpu 486,-fpu.
>>>>>
>>>>
>>>> Avi,
>>>>
>>>> Running this command:
>>>> qemu-system-x86_64 -net nic,model=rtl8139 -net user -hda $1 
>>>> -no-acpi -usb -cpu 486,-fpu &
>>>>
>>>> I get a seg fault:
>>>> qemu-system-x86[15419]: segfault at c ip 0000000000458b95 sp 
>>>> 0000000041d9df90 error 4 in qemu-system-x86_64[400000+208000]
>>>>
>>>>
>>>> I am running kvm-87 centos 5.3 x86_64.
>>>
>>> Add -no-kvm-irqchip.  A 486 doesn't have a local APIC, which the 
>>> code expects.
>>>
>> Running with this line:
>> qemu-system-x86_64 -net nic,model=rtl8139 -net user -hda $1 -no-acpi 
>> -usb -cpu 486,-fpu -no-kvm-irqchip &
>>
>>
>>
>> My /proc/cpuinfo shows the follow:
>> processor       : 0
>> vendor_id       : AuthenticAMD
>> cpu family      : 4
>> model           : 0
>> model name      : 04/00
>> stepping        : 0
>> fdiv_bug        : no
>> hlt_bug         : no
>> f00f_bug        : no
>> coma_bug        : no
>> fpu             : yes
>> fpu_exception   : no
>> cpuid level     : 0
>> wp              : yes
>> flags           :
>> bogomips        : 2965.50
>> clflush size    : 32
>> power management:
>>
>>
>> Notice FPU indicates yes and I requested -fpu on the command line.
>
> I think it detects the host fpu as a 487 coprocessor.  Anything in 
> dmesg about it?  Note there's no fpu in the flags: line.
>
> That's a kvm kernel bug.
>
>> also is this a 486 as it says AMD?
>
> You can override it if you like, -cpu 486,vendor=AuthenticAMD (I think).
>
Sorry - I thought the " -cpu 486,-fpu " was the way to turn off the fpu.
I 'm trying to emulute a 486 sx that has no fpu.
Do I not have the command line correct? qemu-system-x86_64 -net 
nic,model=rtl8139 -net user -hda $1 -no-acpi -usb -cpu 486,-fpu 
-no-kvm-irqchip

the vendor_id is OK just not what I expected to see.

Jerry