Re: SMMU, Unhandled context fault

From: Peng Fan <van.freenix@gmail.com>
To: Julien Grall <julien.grall@arm.com>
Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
	sstabellini@kernel.org, xen-devel@lists.xenproject.org
Subject: Re: SMMU, Unhandled context fault
Date: Thu, 28 Apr 2016 14:39:27 +0800	[thread overview]
Message-ID: <20160428063924.GA28064@linux-7smt.suse> (raw)
In-Reply-To: <20160428023752.GA4898@linux-7smt.suse>

Hi Julien,

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 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.

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.

Thanks,
Peng.

>
>Thanks,
>Peng.
>
>>
>>Regards,
>>
>>-- 
>>Julien Grall

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