On 10/25/12 7:12 PM, Ilija Hadzic wrote:
On Thu, Oct 25, 2012 at 11:10 AM, Thomas Hellström
<thellstrom@xxxxxxxxxx> wrote:
On 10/25/12 4:41 PM, Jerome Glisse wrote:
On Thu, Oct 25, 2012 at 04:02:25PM +0200, Thomas Hellstrom wrote:
Hi,
This commit
From 949c4a34afacfe800fc442afac117aba15284962 Mon Sep 17 00:00:00 2001
From: Ilija Hadzic <ihadzic@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 15 May 2012 16:40:10 -0400
Subject: [PATCH] drm: track dev_mapping in more robust and flexible way
Setting dev_mapping (pointer to the address_space structure
used for memory mappings) to the address_space of the first
opener's inode and then failing if other openers come in
through a different inode has a few restrictions that are
eliminated by this patch.
If we already have valid dev_mapping and we spot an opener
with different i_node, we force its i_mapping pointer to the
already established address_space structure (first opener's
inode). This will make all mappings from drm device hang off
the same address_space object.
...
Breaks drivers using TTM, since when the X server calls into the
driver open, drm's dev_mapping has not
yet been setup. The setup needs to be moved before the driver's open
hook is called.
Typically, if a TTM-aware driver is provoked by the Xorg server to
move a buffer from system to VRAM or AGP,
before any other drm client is started, The user-space page table
entries are not killed before the move, and left pointing
into freed pages, causing system crashes and / or user-space access
to arbitrary memory.
Doesn't handle move invalidate the drm file mapping before scheduling
the move ?
Yes, but to do that it needs a correct value of bdev::dev_mapping, which is
now incorrectly set on the
*second* open instead of the first open.
So you are implying that in the first open the assignment of dev->dev_mapping is
somehow skipped (which could happen if drm_setup returns an error) or that the
driver on which you are having problems with (nouveau I presume) needs
dev_mapping
in the firstopen hook ?
No. On open, driver::open is called from drm::open. It copies the value
of dev->dev_mapping, however,
driver::open is called *before* dev->dev_mapping is set up, so what I'm
saying is that the setup of
dev->dev_mapping must be moved to before driver::open is called from
drm::open
(this was hit while testing vmwgfx with new code, BTW. It will be hard,
but probably possible to trigger
from unpriviliged user-space with the current vmwgfx code.
Thanks,
Thomas
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