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

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> >> > 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?
> 
> Not within today's Xen or Linux (which both assume a global kernel
> address space, in particular non-root page table entries 
> mapping kernel
> space to be the same in all address spaces - you'd need 
> separate entries
> at all levels for this).

OK, I forgot: No software-accessible TLB.

Can you think of any trick (that doesn't require the cost of a
trap/hypercall) to allow an app to determine what pcpu
it is running on?

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