Re: [Qemu-devel] Re: SVM support in 0.12?

[Andre Przywara]

Andre Przywara wrote:
> Jun Koi wrote:
> > > > > > > I am running latest Qemu 0.12-rc. My guest VM runs Linux kernel 
> > > > > > > 2.6.31.
> > > > > > >
> > > > > > > Because Qemu now supports SVM, I expect to see the SVM flag in
> > > > > > > /proc/cpuinfo, but that is not the case.
> > > > > > >
> > > > > > > So it seems SVM support is not enabled by default configuration??
> > > > > > My host and guest are both 32 bit Linux, if that matters.
> > > > > >
> > > > > > (And this is pure Qemu, without using KVM or KQemu)
> > > > > Kqemu actually works with svm emulation.
> ...
> > > > qemu -m 500 -cpu qemu32,+svm -cdrom ubuntu.iso
> > > >
> > > > I verified that /proc/cpuinfo has no svm flag. So SVM doesnt work on 
> > > > 32bit
> > > > host.
> > > >
> > > > I will try that with 64bit host to see how it goes.
> > > The host doesn't matter. You can easily run qemu-system-x86_64 on a 
> > > 32-bit
> > > host.
> >
> > I can confirm that SVM works well on x86-64 target, but fails on i386 
> > target.
>
> The Linux kernel will only detect SVM if the machine is AMD (see 
> linux-2.6/arch/x86/include/asm/virtext.h:cpu_has_svm())
> So please try:
> $ qemu -m 500 -cpu qemu32,+svm,vendor=AuthenticAMD -cdrom ubuntu.iso
> (because the default vendor for qemu32 is Intel, for qemu64 AMD)

Should have checked this before the post ;-):
qemu32 has a xlevel of 0, so no AMD-defined CPUID leafs will be parsed.
Either fix this explicitly with xlevel=0xa or use athlon as your base 
CPU model:
$ qemu -m 500 -cpu athlon,+svm -cdrom ubuntu.iso

This made my Linux show the SVM flag.

Regards,
Andre.

--
Andre Przywara
AMD-OSRC (Dresden)
Tel: x29712