RE: [PATCH] iommufd: Fix wrong hwpt passed to iommufd_auto_response_faults on replace

[Tian, Kevin]

> From: Peiyang He <peiyang_he@xxxxxxxxxxxxxxxx>
> Sent: Friday, July 10, 2026 8:30 PM
>
> iommufd_hwpt_replace_device() calls:
> 
> 	iommufd_auto_response_faults(hwpt, old_handle);
> 
> passing the *new* hwpt together with the handle of
> the device's *old* domain. This should be a parameter mismatch:
> 
> 1. Semantically, iommufd_auto_response_faults(x, handle) scans
>    x->fault's deliver list and response xarray for groups matching
>    "handle". A group is queued under the hwpt that was attached at
>    fault-delivery time. old_handle is fetched *before* the domain switch,
>    so its group lives on old->fault, not on the new hwpt->fault.
> 
> 2. Historically, the first argument was "old". The routine was
>    introduced by commit b7d8833677ba ("iommufd: Fault-capable hwpt
>    attach/detach/replace") as __fault_domain_replace_dev() in
>    fault.c, correctly calling iommufd_auto_response_faults(old, curr).
>    Commit fb21b1568ada ("iommufd: Make attach_handle generic than
>    fault specific") moved this into iommufd_hwpt_replace_device() in
>    device.c and swapped it to "hwpt". This should be a refactor regression,
>    not an intentional change.
> 
> Fix this by passing "old" instead.
> 
> Reported-by: Peiyang He <peiyang_he@xxxxxxxxxxxxxxxx>

ditto not required.

> Fixes: fb21b1568ada ("iommufd: Make attach_handle generic than fault
> specific")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Peiyang He <peiyang_he@xxxxxxxxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>