Re: [REGRESSION] GPU passes into VM improperly after c376a3456d8b or a98db518dde2

[Baolu Lu <baolu.lu@linux.intel.com>]

On 4/27/2026 3:15 PM, Baolu Lu wrote:
> On 4/14/26 17:22, 70sp wrote:
>> I can confirm, that the "domain is not compatible with device" message 
>> is nowhere to be seen.
>>
>> I have double checked by also adding an else statement with a 
>> different message and that one showed up several times. (by pci (iGPU) 
>> 0000:00:02.0, pcieport 0000:00:01.0 and vfio-pci (GTX 970) 
>> 0000:01:00.0, 0000:01:00.1). ret = 0.
>>
> 
> Hmm, it seems the domain is compatible with the device hardware and was
> attached successfully. Perhaps you can try to check the differences
> between these two domain attachments by dumping the root, context, and
> PASID table entries and comparing the configurations of the success and
> failure cases.
> 
> To do this, simply apply the change below with CONFIG_DMAR_DEBUG
> enabled:
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 4d0e65bc131d..bf303cfcf2ee 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1345,6 +1345,9 @@ static int dmar_domain_attach_device(struct 
> dmar_domain *domain,
>          if (ret)
>                  goto out_block_translation;
> 
> +       dmar_fault_dump_ptes(iommu, PCI_DEVID(info->bus, info->devfn),
> +                            0, IOMMU_NO_PASID);
> +
>          return 0;
> 
>   out_block_translation:

Have you tried this patch? It dumps the context and PASID table entries
after a domain is attached to the device. Hopefully, you can find some
clues by comparing the good and bad kernels.

Thanks,
baolu