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[Xen-devel] Re: rdtsc: correctness vs performance on Xen (and KVM?)
| To: | Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
|---|---|
| Subject: | [Xen-devel] Re: rdtsc: correctness vs performance on Xen (and KVM?) |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Tue, 01 Sep 2009 16:08:37 +0100 |
| Cc: | "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> |
| Delivery-date: | Tue, 01 Sep 2009 08:09:13 -0700 |
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| Thread-topic: | rdtsc: correctness vs performance on Xen (and KVM?) |
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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 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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