SEP regression in kvm-20?

SEP regression in kvm-20?

[Rusty Russell]

Hi all,

	I note that Linux under kvm 20 doesn't use sysenter, while it did under
kvm 19.  There's no "sep" in /proc/cpuinfo and the vendor id looks kinda
random too: this looks like a cpuid problem?

Cheers,
Rusty.


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Re: SEP regression in kvm-20?

[Avi Kivity]

Rusty Russell wrote:
> Hi all,
>
> 	I note that Linux under kvm 20 doesn't use sysenter, while it did under
> kvm 19.  There's no "sep" in /proc/cpuinfo 

x86info does report sep, but arch/i386/kernel/cpu/intel.c has this to say:

        /* SEP CPUID bug: Pentium Pro reports SEP but doesn't have it 
until model 3 mask 3 */
        if ((c->x86<<8 | c->x86_model<<4 | c->x86_mask) < 0x633)
                clear_bit(X86_FEATURE_SEP, c->x86_capability);

whereas our cpu is

        cpu family      : 6
        model           : 2

so, no SEP for you.  I imagine we can bump the model and mask to 3.

> and the vendor id looks kinda
> random too: this looks like a cpuid problem?
>   

I see a

        vendor_id       : GenuineIntel

?

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


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Re: SEP regression in kvm-20?

[Rusty Russell]

On Mon, 2007-04-23 at 10:17 +0300, Avi Kivity wrote:
> Rusty Russell wrote:
> > Hi all,
> >
> > 	I note that Linux under kvm 20 doesn't use sysenter, while it did under
> > kvm 19.  There's no "sep" in /proc/cpuinfo 
> 
> x86info does report sep, but arch/i386/kernel/cpu/intel.c has this to say:
> 
>         /* SEP CPUID bug: Pentium Pro reports SEP but doesn't have it 
> until model 3 mask 3 */
>         if ((c->x86<<8 | c->x86_model<<4 | c->x86_mask) < 0x633)
>                 clear_bit(X86_FEATURE_SEP, c->x86_capability);
> 
> whereas our cpu is
> 
>         cpu family      : 6
>         model           : 2
> 
> so, no SEP for you.  I imagine we can bump the model and mask to 3.

Hi Avi!

	Seems strange that this changed between kvm 19 and kvm 20.
kvm-20/qemu/target-i386/helper2.c seems to offer 6/3/3.

> > and the vendor id looks kinda
> > random too: this looks like a cpuid problem?
> >   
> 
> I see a
> 
>         vendor_id       : GenuineIntel

vendor_id here is a char 223:

processor       : 0
vendor_id       : �
cpu family      : 0
model           : 2
model name      : 00/02
stepping        : 8
cpu MHz         : 2835.485
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 65535
wp              : yes
flags           : fpu vme tsc mce up pni monitor ds_cpl vmx smx est tm2
ssse3 cid cx16 xtpr
bogomips        : 4207.41
clflush size    : 32

FYI, Host is:

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Core(TM)2 CPU          6400  @ 2.13GHz
stepping        : 6
cpu MHz         : 2128.059
cache size      : 2048 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 2
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
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 nx lm
constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm
bogomips        : 4258.53
clflush size    : 64

Cheers,
Rusty.


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Re: SEP regression in kvm-20?

[Avi Kivity]

Rusty Russell wrote:
> vendor_id here is a char 223:
>
> processor       : 0
> vendor_id       : �
>   

I fixed an assembly constraint problem (& pushed to kernel.org) which 
may help with this.

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


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