Re: SMMU, Unhandled context fault

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

On 25/04/2016 09:54, Peng Fan wrote:
> Hi Julien, Stefano

Hello Peng,

> I met an issue when passthrough a device to DomU, and have no clear idea what's wrong.

Which version of the SMMU is present on the board? Is it SMMUv1 or SMMUv2?

The SMMU drivers in Xen has been ported from Linux last year. It might 
be possible that some bug fixes need to be ported.

> "
> (XEN) smmu: /iommu@5c800000: Unhandled context fault: iova=0x42188000, fsynr=0x433, cb=0
> (XEN) smmu: /iommu@5c800000: Unhandled context fault: iova=0x42188020, fsynr=0x433, cb=0
> "

The IOVA corresponds to a guest RAM address. It would be useful if you 
provide the Xen boot logs.

> fsynr is 0x433, PTWF is 1, which means
> "An external fault occurred while processing a translation table walk"
>
> My DomU cfg is:
> "
> kernel = "/root/xen/Image"
> device_tree = "/root/xen/sdhc.dtb"
> dtdev = [ "/usdhc@5a240000" ]
> iomem = [ "0x5a240,0x10@0x1a240"]
> irqs = [ 257 ]
> memory = "128"
> name = "domU-sdhc-test"
> vcpus = 1
> serial="pty"
> disk = [ 'phy:/dev/loop0,xvda,w' ]
> extra = "console=hvc0 root=/dev/xvda debug=/bin/sh"
> "
>
> I saw this patch: http://www.gossamer-threads.com/lists/xen/devel/428030
> "xen/arm: Force broadcast of TLB and instruction cache maintenance instructions"
> So I guess should we have a similar fix for SMMU TLB?

That is different.

Xen only supports SMMU for stage-2 page table, so the hypervisor is in 
charge of flushing the SMMU TLBs when the translation IPA -> PA is changed.

The patch "xen/arm: Force broadcast..." will set HCR_EL2.FB to upgrade 
any local flush instruction made by a guest into innershareable flush 
instruction.

>  From my failure log, It should be that TCU can not find the machine address for iova(guest physical address).

What do you mean by TCU?

Regards,

-- 
Julien Grall

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