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From: Roland Dreier <>
To: Jason Gunthorpe <>
Cc: Hugh Dickins <>,,
	Andrea Arcangeli <>,,
Subject: Re: [PATCH/RFC G-U-P experts] IB/umem: Modernize our get_user_pages() parameters
Date: Mon, 30 Jan 2012 11:19:18 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Sat, Jan 28, 2012 at 11:25 AM, Jason Gunthorpe
<> wrote:
> I know accessing system memory (eg obtained via mmap on
> /sys/bus/pci/devices/0000:00:02.0/resource0) has been asked for in the
> past, and IIRC, the problem was that some of the common code, (GUP?)
> errored on these maps. I don't know if Roland's case is similar.

I think the problem there is that this is done via remap_pfn_range()
or similar, and the mapping has no underlying pages at all.  So we
would need a new interface that gives us different information for
such cases.

This is quite a bit trickier since I don't think the DMA API even has
a way to express getting a "device A" bus address for some memory
that is in a BAR for "device B".  So I'm not trying to address this case
(yet).  First I'd like to deal with as many flavors of page-backed
mappings as I can.

 - R.

  reply	other threads:[~2012-01-30 19:19 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-26  5:59 [PATCH/RFC G-U-P experts] IB/umem: Modernize our get_user_pages() parameters Roland Dreier
2012-01-26 20:01 ` Hugh Dickins
2012-01-26 22:45   ` Roland Dreier
2012-01-27 17:28     ` Roland Dreier
2012-01-28  2:31       ` Hugh Dickins
2012-01-28 19:25         ` Jason Gunthorpe
2012-01-30 19:19           ` Roland Dreier [this message]
2012-01-28  2:19     ` Hugh Dickins
2012-01-30 19:16       ` Roland Dreier
2012-01-30 20:20         ` Andrea Arcangeli
2012-02-06 17:46           ` Roland Dreier
2012-01-30 20:34         ` Hugh Dickins
2012-02-06 17:39           ` Roland Dreier
2012-02-07 20:39             ` Hugh Dickins
2012-02-08 23:10               ` Hugh Dickins
2012-02-09 17:50                 ` Roland Dreier
2012-02-09 22:57                   ` Hugh Dickins

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