Messages in this thread | | | Date | Wed, 25 Mar 2009 18:38:50 +0100 | From | Ingo Molnar <> | Subject | Re: 2.6.29: can't resume from suspend with DMAR (intel iommu) enabled |
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* mark gross <mgross@linux.intel.com> wrote:
> 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.
it's hugely problematic to panic() the box early during bootup. IOMMU code should be disabled instead, a warning emitted - and life should continue.
With the current method you only ensure that distros turn DMAR support off and that users disable it in their BIOS. That's a double disadvantage.
Ingo
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