From: Roland Dreier <roland@kernel.org>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Hugh Dickins <hughd@google.com>,
linux-rdma@vger.kernel.org,
Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
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: <CAL1RGDWm6q9SxO_X5PR8Z7_V6wiYmoHqdPfX++8=Ph1v5HiZ6Q@mail.gmail.com> (raw)
In-Reply-To: <20120128192553.GA16231@obsidianresearch.com>
On Sat, Jan 28, 2012 at 11:25 AM, Jason Gunthorpe
<jgunthorpe@obsidianresearch.com> 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.
next prev parent 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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