DMA on stack?

[Dan Williams]

On Tue, 2007-11-13 at 11:14 -0800, Pete Zaitcev wrote:
> On Tue, 13 Nov 2007 10:09:58 -0500, Dan Williams <dcbw at redhat.com> wrote:
> > On Tue, 2007-11-13 at 16:10 +0100, Oliver Neukum wrote:
> 
> > > has anybody verified that this code: (if_usb.c::if_usb_suspend)
> 
> > > 		libertas_prepare_and_send_command(priv,
> > > 				CMD_MESH_ACCESS,
> > > 				CMD_ACT_MESH_SET_AUTOSTART_ENABLED,
> > > 				CMD_OPTION_WAITFORRSP, 0, (void *)&mesh_access);
> > > 
> > > does not do DMA on the stack?
> > 
> > I don't think so, no.
> 
> XO uses an x86 compatible non-SMP AMD CPU, so there's no problem with
> DMA to stack. If they had an SMP x86_64 or ARM, they'd find this
> in 5 minutes. BTW, where did you find that? I'd like to have a look

It should just be in wireless-2.6/everything as well as 2.6.23.  Note
that all patches that are completely OLPC specific are in the OLPC
kernel git tree, and what's in wireless-2.6 is fully functional and
suitable for upstream without OLPC private ioctls and such.  olpc-2.6
notably has a lot of the custom suspend/resume hacks that were necessary
for fast suspend/resume on XO hardware, which wireless-2.6 doesn't have
for obvious reasons.

However, if there's a possibility that the above snipped could have
problems on CPUs other than the XOs, we should figure out a way to fix
it.  It's not too high a priority since there aren't any 8388 USB
dongles out there other than the reference boards that a few people have
(and the mesh firmware only runs on 8388 parts), but it should still get
fixed for correctness' sake.

Dan

> too due to issues with the disconnect dwmw2 mentioned the other day.
> Marcelo only showed me fragments.
> 
> -- Pete