Re: [Xen-users] amd processors + virtualisation

[Thomas Harold <tgh@xxxxxxxxxxxx>]

Petersson, Mats wrote:
> > On the newer CentOS5 boxes using AM2 Athlon64 X2 and SocketF Opteron 
> > CPUs, the default CentOS5 kernel does allow the "svm" flag to peek 
> > through.  And I have not installed virtualization support on 
> > this box (yet).
> Presumably, you have a recent enough kernel now (it's been in there for
> quite some time, I spent a few minutes trying to locate the version
> where it went in, but I (using google) wasn't able to find it...)
Ah, that makes sense.  (Goes poking through his session logs...)

Here's the original install, probably using Gentoo 2006.0 w/ the 2.6.15 
kernel (but Gentoo's version).  As you can see, the grep didn't find the 
"svm" flag.
livecd ~ # cat /proc/cpuinfo | grep 'flags'
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge 
mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mm
xext fxsr_opt lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy

livecd ~ # cat /proc/cpuinfo | grep 'svm'
livecd ~ # cat /proc/version
Linux version 2.6.15-gentoo-r5 (root@poseidon) (gcc version 3.4.4 
(Gentoo 3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)) #1 SMP Tue Feb 21 17:
19:47 UTC 2006
livecd ~ #

Here's an entry from the next day after upgrading to 2.6.17.  This one 
shows the "svm" flag.
azure ~ # cat /proc/version
Linux version 2.6.17-gentoo-r4 (root@livecd) (gcc version 3.4.4 (Gentoo 
3.4.4-r1, ssp-3.4.4-1.0, pie-8.7.8)) #1 SMP Sat Aug 26 00:34
:30 EDT 2006

livecd ~ # cat /proc/cpuinfo | grep 'flags'
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge 
mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mm
xext fxsr_opt lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm cr8_legacy

So it was probably either 2.6.16 or 2.6.17 where the code for the "svm" 
flag was added.
...

I wasn't sure how the kernel detected those flags.  I didn't know 
whether it was special detection code (which had to be updated for new 
features) or whether the processor spit back a string listing.
Thanks for the responses.

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