Re: [Xen-devel] SMMU, Unhandled context fault

[Julien Grall <julien.grall@xxxxxxx>]

On 28/04/16 07:39, Peng Fan wrote:
> Hi Julien,
Hello Peng,

> On Thu, Apr 28, 2016 at 10:37:54AM +0800, Peng Fan wrote:
> > Hi Julien,
> > On Wed, Apr 27, 2016 at 10:58:28AM +0100, Julien Grall wrote:
> > > Hello Peng,
> > >
> > > On 27/04/2016 03:02, Peng Fan wrote:
> > > > On Tue, Apr 26, 2016 at 04:30:03PM +0200, Edgar E. Iglesias wrote:
> > > > > On Tue, Apr 26, 2016 at 09:56:33PM +0800, Peng Fan wrote:
> > > > > > You mean the PNU bit(Privileged Not Unprivileged) is 1?
> > > > > > I did not met Unhandled context fault each time.
> > > > > > Actually during my serveral boot test, I only met two times.
> > > > >
> > > > >
> > > > > I meant the NSSTATE and NSATTR bits in FSYNR are set to zero. I get the
> > > > > impression that the TrustZone state for the SD controller may be
> > > > oh. The NSATTR bit is 0. I did not find NSSTATE in my Issue D SMMU spec.
> > > > If without xen, only one linux boots up, sd controller can access memory using
> > > > DMA without issue.
> > > IIRC, by default Linux baremetal does not protect the devices with the SMMU.
> > >
> > > I would recommend you to check whether the SMMUs are in-used and configured
> > > to generate a fault (disable_bypass = 1).
> > Ok. I'll set S2CRn to generate fault in xen smmu driver to see whether SMMUs 
> > in-used or not
I meant in Linux.

> > I found a patch for errata of mmu-500,
> > https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/commit/?h=iommu/devel&id=7f0cc5124f5ec66b5b26878ac85137adc6537413
> > Do you know this?
> >
> > I suspect the unstable issue on my platform seems related to this errata,
> > but i do not have details about this errata.
Have you tried to port the patch to Xen and see if it helps?

> I do the following change:
>         //s2cr = S2CR_TYPE_TRANS | S2CR_PRIVCFG_UNPRIV |
>          s2cr = S2CR_TYPE_FAULT | S2CR_PRIVCFG_UNPRIV |
>                 (smmu_domain->cfg.cbndx << S2CR_CBNDX_SHIFT);
>
> Now XEN SMMU driver reports that:
> (XEN) smmu: /iommu@5c800000: Unexpected global fault, this could be serious
> (XEN) smmu: /iommu@5c800000:    GFSR 0x00000001, GFSYNR0 0x00000004, GFSYNR1 
> 0x00000011, GFSYNR2 0x00000000
>
> So I think SMMU is working.
Well, it does not help to know whether the SMMU has been correctly 
initialized by Xen.
Regards,

--
Julien Grall

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