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 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


--
Regards,
Yi Liu



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