On Thu, Aug 22, 2013 at 09:12:40AM +0200, Maarten Lankhorst wrote:
Op 22-08-13 02:10, Ilia Mirkin schreef:
The code expects non-VRAM mem nodes to have a pages list. If that's not set, it will do a null deref down the line. Warn on that condition and return an error.
See https://bugs.freedesktop.org/show_bug.cgi?id=64774
Reported-by: Pasi Kärkkäinen pasik@iki.fi Tested-by: Pasi Kärkkäinen pasik@iki.fi Signed-off-by: Ilia Mirkin imirkin@alum.mit.edu Cc: stable@vger.kernel.org # 3.8+
I don't exactly understand what's going on, but this is just a straightforward way to avoid a null deref that you see happens in the bug. I haven't figured out the root cause of this, but it's getting well into the "I have no idea how TTM works" space. However this seems like a bit of defensive programming -- nouveau_vm_map_sg will pass node->pages as a list down, which will be dereferenced by nvc0_vm_map_sg. Perhaps the other arguments should make that dereferencing not happen, but it definitely was happening here, as you can see in the bug.
Ben/Maarten, I'll let you judge whether this check is appropriate, since like I hope I was able to convey above, I'm just not really sure :)
Not it really isn't appropriate..
You'd have to call call nouveau_vm_map_sg_table instead, the only place that doesn't handle that correctly is where it's not expected to be called.
Here, have a completely untested patch to fix things...
Maarten: I've been testing this stuff with Linux 3.10.x, so I had to modify the patch a bit to make it apply there.. I've attached the modified copy that applies to 3.10.9, hopefully I did the backport correctly.
With Linux 3.10.9 and the patch applied the kernel doesn't crash anymore, and I get this error in dmesg:
[ 76.105643] nouveau W[ DRM] Trying to create a fb in vram with valid_domains=00000004
Does that help?
-- Pasi