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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

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.

> 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?

 -- Keir



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