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Re: [Xen-devel] Re: how to handle paged hypercall args?

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] Re: how to handle paged hypercall args?
From: Keir Fraser <keir@xxxxxxx>
Date: Fri, 12 Nov 2010 14:32:16 +0000
Cc: Olaf Hering <olaf@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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Thread-topic: [Xen-devel] Re: how to handle paged hypercall args?
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On 12/11/2010 10:47, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

>>>> On 12.11.10 at 11:22, Keir Fraser <keir@xxxxxxx> wrote:
>> On 12/11/2010 09:45, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>> Beyond that, introducing some transparent mechanisms for sleeping in the
>> hypervisor -- mutexes, wait queues, and the like -- is actually fine with
>> me. Perhaps this will also help clean up the preemptible page-type-checking
>> logic that you had to do some heavy lifting on?
> I'm not sure it would help there - this requires voluntary
> preemption rather than synchronization. But perhaps it can be
> built on top of this (or results as a side effect).

Yes, voluntary preempt can be built from the same bits and pieces very
easily. I will provide that too, and I think some simplification to the
page-type functions and callers will result. No bad thing!

>> I'm happy to help work on the basic mechanism of this, if it's going to be
>> useful and widely used. I reckon I could get mutexes and wait queues going
>> in a couple of days. This would be the kind of framework that the paging
>> mechanisms should then properly be built on.
>> What do you think?
> Sounds good, and you helping with this will be much appreciated
> (Olaf - unless you had plans doing this yourself). Whether it's going
> to be widely used I can't tell immediately - for the moment,
> overcoming the paging problems seems like the only application.

Yeah, I'll get on this.

 -- Keir

> Jan

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