Re: [BUG + PATCH/Bugfix] x86/lguest: fix pgdir pmd index calculation

Rusty Russell
2008-03-04T06:38:17Z

On Saturday 01 March 2008 06:58:38 Ingo Molnar wrote:
> * Ahmed S. Darwish <darwish.07@gmail.com> wrote:
> > On the lguest _guest_ side, 'cpu_has_tsc' is _always_ false (due to
> > lguest using his own clocksource ?), thus a guest with a pentium+ cpu
> > always panics with:
>
> does the "RDTSC" instruction work in an lguest guest? If not, then the
> lguest kernel is correct in not exposing it - and then the solution is
> to build a non-TSC guest kernel. Does the patch below help?
>
> but if the RDTSC instruction does work in an lguest guest, then the
> proper approach would be to expose it in the CPU features.
>
> Ingo

It does (assuming host support), but when I tried to use the normal TSC code
it poked at other things which a guest couldn't do.

Currently I've hit another issue, but revisiting this is on my TODO. The
cpu_has_tsc panic is overzealous, since we deal without it, but it'd be nice
to use the common TSC clock code.

Thanks,
Rusty.