kvm guest for 486 sx

kvm guest for 486 sx

[Jerry Geis]

I wish to run as a guest a 486 SX equivalent
is there an option to disable the floating point support?

Is it possible to do this?

Thanks,

Jerry

Re: kvm guest for 486 sx

[Avi Kivity]

On 07/06/2009 10:58 PM, Jerry Geis wrote:
> I wish to run as a guest a 486 SX equivalent
> is there an option to disable the floating point support?
>
> Is it possible to do this?
>

Try -cpu 486,-fpu.

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

Re: kvm guest for 486 sx

[Jerry Geis]

Avi Kivity wrote:
> On 07/06/2009 10:58 PM, Jerry Geis wrote:
>> I wish to run as a guest a 486 SX equivalent
>> is there an option to disable the floating point support?
>>
>> Is it possible to do this?
>>
>
> 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.

Jerry

Re: kvm guest for 486 sx

[Avi Kivity]

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.

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

Re: kvm guest for 486 sx

[Jerry Geis]

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.
>
This works. Thanks.

Jerry

Re: kvm guest for 486 sx

[Jerry Geis]

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.
also is this a 486 as it says AMD?

Thanks,

Jerry

Re: kvm guest for 486 sx

[Avi Kivity]

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).

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

Re: kvm guest for 486 sx

[Jerry Geis]

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

Re: kvm guest for 486 sx

[Avi Kivity]

On 07/07/2009 04:15 PM, Jerry Geis wrote:
>>> 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.

I thought so too, but in fact it emulates a 486sx+487.  We can make it 
emulate a 486sx without a 487, but that will take a kernel patch.

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

Re: kvm guest for 486 sx

[Jerry Geis]

Avi Kivity wrote:
> On 07/07/2009 04:15 PM, Jerry Geis wrote:
>>>> 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.
>
> I thought so too, but in fact it emulates a 486sx+487.  We can make it 
> emulate a 486sx without a 487, but that will take a kernel patch.
>
I'd be interested in that if you can make it happen.

jerry

Re: kvm guest for 486 sx

[Avi Kivity]

On 07/07/2009 05:58 PM, Jerry Geis wrote:
>> I thought so too, but in fact it emulates a 486sx+487.  We can make 
>> it emulate a 486sx without a 487, but that will take a kernel patch.
>
> I'd be interested in that if you can make it happen.

I don't think I'll get around to it soon.  I'll happily apply a patch 
though.

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

Re: kvm guest for 486 sx

[Jerry Geis]

Avi Kivity wrote:
> On 07/07/2009 05:58 PM, Jerry Geis wrote:
>>> I thought so too, but in fact it emulates a 486sx+487.  We can make 
>>> it emulate a 486sx without a 487, but that will take a kernel patch.
>>
>> I'd be interested in that if you can make it happen.
>
> I don't think I'll get around to it soon.  I'll happily apply a patch 
> though.
>

I wish  could. I'll have to wait or you.

jerry

Re: kvm guest for 486 sx

[Andre Przywara]

Avi Kivity wrote:
> On 07/07/2009 04:15 PM, Jerry Geis wrote:
>>>> 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.
> 
> I thought so too, but in fact it emulates a 486sx+487.
-fpu does not help here, as the injected 486 CPUID limits the level to 
0, so effectively no other leaf than leaf 0 is checked by the guest. 
That's why the FPU bit, which is 0000_0001.EDX:0, is not honored.
I bumped up the level to 1 and set the model to 2, which should mimic a 
later 486SX chip, together with -fpu Linux (2.6.21) still insisted on 
fpu: yes (probably determined by probing FPU instructions).
 >  We can make it
> emulate a 486sx without a 487, but that will take a kernel patch.
What are you thinking of? Forcing CR0.EM to 1 (and don't let the guest 
change it), then inject #NM into the guest?

Regards,
Andre.

-- 
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448 3567 12
----to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
Geschaeftsfuehrer: Thomas M. McCoy; Giuliano Meroni
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632

Re: kvm guest for 486 sx

[Avi Kivity]

On 07/08/2009 02:04 PM, Andre Przywara wrote:
>
>> emulate a 486sx without a 487, but that will take a kernel patch.
> What are you thinking of? Forcing CR0.EM to 1 (and don't let the guest 
> change it), then inject #NM into the guest?

Yes.

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

Re: kvm guest for 486 sx

[Gleb Natapov]

On Tue, Jul 07, 2009 at 08:06:10AM -0400, Jerry Geis wrote:
> Avi Kivity wrote:
>> On 07/06/2009 10:58 PM, Jerry Geis wrote:
>>> I wish to run as a guest a 486 SX equivalent
>>> is there an option to disable the floating point support?
>>>
>>> Is it possible to do this?
>>>
>>
>> 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.
>
Apply the patch and try again please.


diff --git a/hw/apic.c b/hw/apic.c
index 778a853..3e79377 100644
--- a/hw/apic.c
+++ b/hw/apic.c
@@ -955,7 +955,8 @@ static void kvm_kernel_lapic_load_from_user(APICState *s)
 void qemu_kvm_load_lapic(CPUState *env)
 {
 #ifdef KVM_CAP_IRQCHIP
-    if (kvm_enabled() && kvm_vcpu_inited(env) && qemu_kvm_irqchip_in_kernel()) {
+    if (kvm_enabled() && kvm_vcpu_inited(env) &&
+		    qemu_kvm_irqchip_in_kernel() && env->apic_state) {
         kvm_kernel_lapic_load_from_user(env->apic_state);
     }
 #endif
--
			Gleb.