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Need help to debug Arm SMMU issue seen on guests with passthrough devices


  • To: Rahul Singh <rahul.singh@xxxxxxx>, ", Bertrand Marquis" <Bertrand.Marquis@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, ", Volodymyr Babchuk" <Volodymyr_Babchuk@xxxxxxxx>
  • From: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxxxxx>
  • Date: Thu, 21 Apr 2022 12:12:14 +0100
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  • Delivery-date: Thu, 21 Apr 2022 11:12:23 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

Hi Arm/SMMU experts,

Scenario :- I am trying to assign a device (eg mmc) to a guest which uses smmu. I start the guest using "xl create -c ...". It works fine for the first time. I am able to access the device.

Now, when I destroy the guest and create again, I see this issue

(XEN) smmu: /axi/smmu@fd800000:         GFSR 0x00000002, GFSYNR0 0x00000000, GFSYNR1 0x00000871, GFSYNR2 0x00000000

0x871 is the stream id used by mmc.

We are using SMMU-500. So from the Arm SMMU v2 specs, it is "Unidentified stream fault" for stream id "0x871".

This issue is seen regardless we use 'mmu-masters' or 'iommus' property in xen device tree.

I can confirm that this issue was not seen in xen-4.14.3. It is seen in our (Xilinx's) latest release ie xen-4.16.1.

I am using our downstream fork of Xen. I can't readily use the upstream as we use lot of EEMI codebase.


Can someone try to see if this issue exists in the latest upstream Xen ?

Any pointers on how to debug this further ?

Kind regards,

Ayan








 


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