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xen-devel
[Xen-devel] RE: pvclock in userland (reprise)
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To: |
Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx> |
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Subject: |
[Xen-devel] RE: pvclock in userland (reprise) |
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From: |
"Nakajima, Jun" <jun.nakajima@xxxxxxxxx> |
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Date: |
Thu, 17 Sep 2009 12:13:49 -0700 |
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en-US |
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en-US |
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Cc: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx>, "Dugger, Donald D" <donald.d.dugger@xxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx> |
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Thu, 17 Sep 2009 12:14:16 -0700 |
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Aco3wIEUOMEVM/j+SGeKFmFaWmbhWgACRF3UAAA5/QA= |
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Thread-topic: |
pvclock in userland (reprise) |
Keir Fraser wrote on Thu, 17 Sep 2009 at 12:03:42:
> On 17/09/2009 18:58, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>
> wrote:
>
>> A remaining hard problem is that this single
>> "userland-accessible shared page" must be somehow
>> made available to apps (I suggested a rdmsr emulated
>> by Xen so that it works in userland) and must be
>> mapped into the app address space without kernel
>> changes. I think someone (Keir?) suggested this
>> problem was solveable before we got sidetracked
>> on the need-vcpu-number-in-userland problem.
> I don't think mapping things into application address space is really
> possible without guest kernel changes. The guest kernel owns and manages
> the pte that you'd be overwriting. Just blatting the pte would not be
> good form.
>
Maybe you can write a device driver in the guest that sets up mapping against
the (virtual) physical memory, then use mmap() in the app?
Jun
___
Intel Open Source Technology Center
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