Re: SMMU, Unhandled context fault

[Julien Grall <julien.grall@arm.com>]

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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