[Xen-devel] RE: rdtsc: correctness vs performance on Xen (and KVM?)

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> On 01/09/2009 15:53, "Dan Magenheimer" 
> <dan.magenheimer@xxxxxxxxxx> wrote:
> 
> > 1) fake rdmsr (or hypercall if it works) returns a virtual
> >    address within a range of addresses that is not "owned by"
> >    the OS (e.g. maybe in Xen address space?).  The page is
> >    only readable outside of ring 0, but writeable in ring 0
> >    (by Xen).
> > 2) All TLB misses on this page are handled directly by Xen
> >    so the OS never sees the address/page.
> 
> I think these are probably possible, at least for a 64-bit 
> hypervisor which
> isn't playing segment limit tricks.

Will it work for pv32_on_64?  (I don't care much about
32-bit hypervisor.)
 
> > If these are OK, and you see other parts of the proposal
> > that require PV kernel mods, please point them out.
> 
> Won't the pvclock computation be per-cpu? How will you deal with
> that?

Hmmm... is it possible for the same virtual address/page
to map to a different physical address/page on each processor?

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