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

[Peng Fan <van.freenix@xxxxxxxxx>]

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 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.

Thanks,
Peng.

>
>Regards,
>
>-- 
>Julien Grall

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