Re: 2.6.29: can't resume from suspend with DMAR (intel iommu) enabled

[mark gross <mgross@linux.intel.com>]

On Tue, Mar 24, 2009 at 09:32:59PM +0100, Ingo Molnar wrote:
> 
> (Cc:s added)
> 
> * Andrew Lutomirski <amluto@gmail.com> wrote:
> 
> > On vanilla 2.6.29 (on Ubuntu 8.10), on a Lenovo x200s, my system 
> > is completely hosed on resume.  It appears that even hard disk IO 
> > didn't work (trying to do *anything* including getting a dmesg 
> > trace just spewed sda io errors to the console).  Hence no trace.  
> > I did an alt-sysrq-b and the screen went blank and the machine 
> > just started beeping at me.
> > 
> > Resume works much better with intel_iommu=off.  (I remember seeing 
> > a patch go by that purported to fix resume with IOMMU enabled, but 
> > it didn't work for me.)
> > 
> > I'd be happy to try to make a better bug report if anyone has any 
> > bright ideas.
> 
> i have a Lenovo T500 that does not even boot with with DMAR enabled 
> in the BIOS (it's default-off), i get this panic in early bootup:
> 
>     DMAR hardware is malfunctioning

That happens when the polling of the IOMMU registers fail to behave as
expected in the VT-d specification.  Typically its been a bios issue
when this happens.

> 
> So i dont get to test suspend/resume ;-)
> 
> 	Ingo