Re: SMMU, Unhandled context fault

[Peng Fan <van.freenix@gmail.com>]

On Thu, Apr 28, 2016 at 11:27:22AM +0100, Julien Grall wrote:
>
>
>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.

My bad. Do you mean enabling SMMU driver in Linux with KVM support?

>
>>>
>>>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 tried. But the value of the register does not change. I am checking with our
IC team.

>
>>
>>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.

Is there any big difference between XEN SMMU driver and linux SMMU driver?
I know that XEN only support Stage 2. But the initliaization flow is almost the same.

Thanks,
Peng.

>
>Regards,
>
>-- 
>Julien Grall

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