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[Xen-devel] questions about get_user_pages()

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] questions about get_user_pages()
From: wei huang <huanwei@xxxxxxxxxxxxxxxxxx>
Date: Tue, 12 Jul 2005 17:05:00 -0400 (EDT)
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I have a question about get_user_pages:

Does the get_user_pages return page_list that can be directly used by
dma_map_sg in xen0? (of course, we do sg[i].page = page_list[i] before
that.) What I actually mean is that if there is any tricky part wrt
pseudo physical address vs actual machine address here.

And I remember once I read that in xen0, the psedudo-physical address and
the actual machine address are the same. Is it still (or ever) the case
for xen-unstable?

If yes, that means nearly all memory operations, eg mapping, dma, etc. can
be performed in xen0 without any problem? Am I right?



On Tue, 12 Jul 2005, Rob Gardner wrote:

> Magenheimer, Dan (HP Labs Fort Collins) wrote:
> >What I propose is that domain0 become the idle domain.  Special
> >casing code would be added to the schedulers so that domain0
> >is always runnable and thus will absorb any "idle" cycles.
> >
> >
> This is admittedly not a grave concern, but doing what you propose will
> screw up performance accounting, since we won't know for sure how much
> cpu time dom0 is really using. And there is reason to believe that dom0
> cpu usage should be closely monitored.
> Rob Gardner
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