Re: Paravirt KVM capabilities

Ingo Molnar
2007-01-11T02:51:30Z

* Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org> wrote:

> > > Err no, this isn't true. See Documentation/lhype.txt or various blog
> > > entries on the subject 8) Both Xen and lhype get native syscall speeds
> > > (within measurement error).
> >
> > i was talking about 64-bit. (we dont really design for 32-bit anymore.)
[...]
>
> > I know that lhype uses Xen's ring 1 trick, but that's a 32-bit-only
> > thing. Also, can SYSENTER trap from guest userspace ring 3 into guest
> > kernelspace ring 1 on lhype?
>
> As I understand it, sysenter has to go to ring 0, and the reflection
> cost is way greater than the saving.

so how can both "Xen and lhype get native syscall speeds (within
measurement error)", if it cannot use SYSENTER (it has to use int
$0x80), while a HVM kernel can?

Ingo