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Re: [Xen-devel] Question on save/restore mfn canonicalization

To: Andres Lagar-Cavilla <andreslc@xxxxxxxxxxxxxx>, John Levon <levon@xxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Question on save/restore mfn canonicalization
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sat, 29 Sep 2007 07:46:30 +0100
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Yeah, it's just the way it got written long ago. It isn't as nice as it
could be, but it can't be changed now.

 -- Keir

On 28/9/07 19:55, "Andres Lagar-Cavilla" <andreslc@xxxxxxxxxxxxxx> wrote:

> Well, when you're in school you don't have to care about breaking ABI's :)
> So, the answer is then "no particular reason"?
> Andres
> John Levon wrote:
>> On Fri, Sep 28, 2007 at 12:25:28PM -0400, Andres Lagar-Cavilla wrote:
>> 
>>   
>>> While exploring the paravirt save/restore code path, I noted a
>>> (seemingly) lack of consistency between where/who canonicalizes
>>> something and who un-canonicalizes. For example, the guest kernel
>>> canonicalizes the store and console mfn's in pre_suspend, but
>>> xc_domain_restore uncanonicalizes them before scheduling back the
>>> restored guest.
>>> The question is if there is a mandatory reason for this, or is just the
>>> way the code was written. Can I, e.g, fill the
>>> pfn_to_mfn_frame_list(_list) entries from "outside" and remove that code
>>> from post_suspend, or will something break?
>>>     
>> 
>> You'll break the ABI. I don't know of a reason why it's so inconsistent.
>> 
>> regards
>> john
>>   
> 
> 
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