RE: [PATCH 5/5 v11] iommu/fsl: Freescale PAMU driver and iommu implementation.

[Yoder Stuart-B08248 <B08248@freescale.com>]

> -----Original Message-----
> From: Sethi Varun-B16395
> Sent: Wednesday, April 03, 2013 12:12 AM
> To: Wood Scott-B07421; Timur Tabi
> Cc: Joerg Roedel; lkml; Kumar Gala; Yoder Stuart-B08248; iommu@lists.linux-foundation.org; Benjamin
> Herrenschmidt; linuxppc-dev@lists.ozlabs.org
> Subject: RE: [PATCH 5/5 v11] iommu/fsl: Freescale PAMU driver and iommu implementation.
> 
> 
> 
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Wednesday, April 03, 2013 7:23 AM
> > To: Timur Tabi
> > Cc: Joerg Roedel; Sethi Varun-B16395; lkml; Kumar Gala; Yoder Stuart-
> > B08248; iommu@lists.linux-foundation.org; Benjamin Herrenschmidt;
> > linuxppc-dev@lists.ozlabs.org
> > Subject: Re: [PATCH 5/5 v11] iommu/fsl: Freescale PAMU driver and iommu
> > implementation.
> >
> > On 04/02/2013 08:35:54 PM, Timur Tabi wrote:
> > > On Tue, Apr 2, 2013 at 11:18 AM, Joerg Roedel <joro@8bytes.org> wrote:
> > >
> > > > > +     panic("\n");
> > > >
> > > > A kernel panic seems like an over-reaction to an access violation.
> > >
> > > We have no way to determining what code caused the violation, so we
> > > can't just kill the process.  I agree it seems like overkill, but what
> > > else should we do?  Does the IOMMU layer have a way for the IOMMU
> > > driver to stop the device that caused the problem?
> >
> > At a minimum, log a message and continue.  Probably turn off the LIODN,
> > at least if it continues to be noisy (otherwise we could get stuck in an
> > interrupt storm as you note).  Possibly let the user know somehow,
> > especially if it's a VFIO domain.
> [Sethi Varun-B16395] Can definitely log the message and disable the LIODN (to avoid an interrupt storm),
> but
> we definitely need a mechanism to inform vfio subsystem about the error. Also, disabling LIODN may not
> be a viable
> option with the new LIODN allocation scheme (where LIODN would be associated with a domain).

I think for phase 1 of this, just log the error, shut down DMA as you described.
We can implement more full featured error management, like notifying vfio
or the VM somehow in the future.

Stuart