linux-kernel - Re: [REGRESSION][BISECTED] PCI Passthrough / SR-IOV Failure on Stable Kernel ≥ v6.12.35

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Message-ID: <82255DF0A021BC1D+513c6ded-088b-4799-8605-b7118c7713ef@bbaa.fun>
Date: Wed, 23 Jul 2025 17:22:44 +0800
From: Ban ZuoXiang <bbaa@...a.fun>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Baolu Lu <baolu.lu@...ux.intel.com>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [REGRESSION][BISECTED] PCI Passthrough / SR-IOV Failure on Stable Kernel ≥ v6.12.35

> Nope!  We need your help as you are the one that can reproduce it :)
>
> Are we missing a backport?  Did we get the backport incorrect?  Should
> we just revert it?
>
> thanks,
> greg k-h

Hi, greg k-h

Original patch:

> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index bb871674d8acba..226e174577fff1 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4298,6 +4306,9 @@ static int identity_domain_attach_dev(struct
> iommu_domain *domain, struct device
>      else
>          ret = device_setup_pass_through(dev);
>  
> +    if (!ret)
> +        info->domain_attached = true;
> +
>      return ret;
>  }
Backport patch:
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 157542c07aaafa..56e9f125cda9a0 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4406,6 +4414,9 @@ static int device_set_dirty_tracking(struct
> list_head *devices, bool enable)
>              break;
>      }
>  
> +    if (!ret)
> +        info->domain_attached = true;
> +
>      return ret;
>  }

The last hunk of the original patch [1] was applied to the
|identity_domain_attach_dev| function, 
but the last hunk of the backport patch [2] appears to have been
mistakenly applied to the |device_set_dirty_tracking| function.
I can confirm that correctly placing the patch from
device_set_dirty_tracking into identity_domain_attach_dev resolves the
issue.

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=320302baed05c6456164652541f23d2a96522c06
[2]
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb5873b779dd5858123c19bbd6959566771e2e83

thanks,
Ban ZuoXiang