Re: DMAR: [DMA Read NO_PASID] Request device [0b:00.0] fault addr 0xffffe000 [fault reason 0x06] PTE Read access is not set

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On 31 December 2022 10:13:37 GMT, Yi Liu <yi.l.liu@xxxxxxxxx> wrote:
>On 2022/12/31 04:07, David Woodhouse wrote:
>> 
>> 
>> On 30 December 2022 19:20:42 GMT, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>>> Hi Major,
>>> 
>>> Thanks for the report!
>>> 
>>> On Wed, Dec 21, 2022 at 08:38:46PM +0530, Major Saheb wrote:
>>>> I have an ubuntu guest running on kvm , and I am passing it 10 qemu
>>>> emulated nvme drives
>>>>      <iommu model='intel'>
>>>>        <driver intremap='on' eim='on'/>
>>>>      </iommu>
>>>> <qemu:arg value='pcie-root-port,id=pcie-root-port%d,slot=%d'/>
>>>> <qemu:arg value='nvme,drive=NVME%d,serial=%s_%d,id=NVME%d,bus=pcie-root-port%d'/>
>>>> 
>>>> kernel
>>>> Linux node-1 5.15.0-56-generic #62-Ubuntu SMP ----- x86_64 x86_64
>>>> x86_64 GNU/Linux
>>>> 
>>>> kernel command line
>>>> intel_iommu=on
>>>> 
>>>> I have attached these drives to vfio-pcie.
>>>> 
>>>> when I try to send IO commands to these drives VIA a userspace nvme
>>>> driver using VFIO I get
>>>> [ 1474.752590] DMAR: DRHD: handling fault status reg 2
>>>> [ 1474.754463] DMAR: [DMA Read NO_PASID] Request device [0b:00.0]
>>>> fault addr 0xffffe000 [fault reason 0x06] PTE Read access is not set
>>>> 
>>>> Can someone explain to me what's happening here ?
>
>You can enable iommu debugfs (CONFIG_INTEL_IOMMU_DEBUGFS=y) to check
>the mapping. In this file, you can see if the 0xffffe000 is mapped or
>not.
>
>/sys/kernel/debug/iommu/intel/domain_translation_struct

My first guess would be that it *was* using queues mapped at that address, but was taken out of the IOMMU domain to be given to userspace, without stopping them.




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