[Xen-devel] Re: TSC scaling and softtsc reprise, and PROPOSAL

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 23/07/2009 16:18, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> pre-VT it wasn't possible to trap RDTSC, so this can't help PV guests.
> 
> For PV guests, CR4.TSD would always be set, generating
> a general protection fault for every rdtsc.  (Or perhaps
> I am missing some x86 architectural subtlety?  This is
> how it is done on ia64.)

Forgot about CR4.TSD. Of course it's not going to be a super fast path,
since #GP(0) will need to be demuxed by decoding the faulting instruction in
the hypervisor, via a not-so-short path.

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel