Re: git-latest: kernel oops in IOMMU setup

[Zhao, Yu]

Dirk Hohndel wrote:
> On Sat, 10 Jan 2009 00:16:22 +0800
> "Zhao, Yu" <yu.zhao@xxxxxxxxx> wrote:
>
> > Dirk Hohndel wrote:
> > > On Fri, 9 Jan 2009 14:53:14 +0800
> > > "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
> > >
> > > > Dirk Hohndel wrote:
> > > > > On Thu, 8 Jan 2009 18:05:15 -0800
> > > > > Dirk Hohndel <hohndel@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > > On Fri, 9 Jan 2009 08:58:46 +0800 "Han, Weidong"
> > > > > >
> > > > > > I updated to Linus' latest git (as your description made me
> > > > > > wonder if the async stuff might play a role here). I still get
> > > > > > an oops - but at a different spot and the system no longer hangs
> > > > > > - it partly recovers (but things aren't too well - for example
> > > > > > my USB keyboard / mouse don't work anymore).
> > > > > Spoke too soon. Rebooted and had the same hard lockup again. This
> > > > > time I had my camera within reach, so here's the trace:
> > > > >
> > > > > device_to_iommu+0x33/0x73
> > > > > domain_context_mapping_one+0x37/0x335
> > > > > domain_context_mapping+0x25/0xa7
> > > > > iommu_prepare_identity+0xd7/0xf3
> > > > > intel_iommu_init+0x4e4/0x8f3
> > > > > ? mutex_lock
> > > > > ? sysctl_net_init
> > > > > ? pci_iommu_init
> > > > > pci_iommu_init
> > > > >
> > > > > I also have stack, code and register values. Let me know if you
> > > > > need them. Or I can just post the picture :-)
> > > > >
> > > > > Again, very latest git tree, VT-d enabled.
> > > > >
> > > > > /D
> > > > I tried latest git tree, it works for me. Above call trace looks
> > > > right. 
> > > Spent some more time reading the code. Can't quite claim to
> > > understand all of it, yet, but I notice that most everywhere else
> > > drhd->devices[i] is checked to be != NULL before it is accessed.
> > > Why is it safe not to do that in device_to_iommu()?
> > >
> > > Would the patch below be a valid fix? It stops my system from
> > > hanging at boot. But I wonder if there is an assertion that if
> > > drhd->ignored is 0 then drhd->devices[0..drhd->device_cnt] is known
> > > to be != NULL and therefore this test is just hiding a bug
> > > somewhere else...
> > >
> > > /D
> > >
> > > Signed-off-by: Dirk Hohndel <hohndel@xxxxxxxxxxxxxxx>
> > > ---
> > >  drivers/pci/intel-iommu.c |    3 ++-
> > >  1 files changed, 2 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
> > > index 235fb7a..3dfecb2 100644
> > > --- a/drivers/pci/intel-iommu.c
> > > +++ b/drivers/pci/intel-iommu.c
> > > @@ -438,7 +438,8 @@ static struct intel_iommu *device_to_iommu(u8
> > > bus, u8 devfn) continue;
> > >  
> > >  		for (i = 0; i < drhd->devices_cnt; i++)
> > > -			if (drhd->devices[i]->bus->number == bus &&
> > > +			if (drhd->devices[i] &&
> > > +			    drhd->devices[i]->bus->number == bus &&
> > >  			    drhd->devices[i]->devfn == devfn)
> > >  				return drhd->iommu;
> > >  
> > Did you see following in the kernel message?
> >                  printk(KERN_WARNING PREFIX
> >                  "Device scope device [%04x:%02x:%02x.%02x] not
> > found\n", segment, scope->bus, path->dev, path->fn);
> >
> > If yes, then
> > 		Acked-by: Yu Zhao <yu.zhao@xxxxxxxxx>
>
> Yes,
>
> DMAR: Device scope device [0000:00:03:02] not found
> DMAR: Device scope device [0000:00:03:02] not found
> DMAR: Device scope device [0000:00:03:03] not found
> DMAR: Device scope device [0000:00:03:03] not found

The laptop has a nasty bios, try to update it if you want to get rid of 
these noises... assuming you are luck enough :-)
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