Re: [PATCH v4] iommu/vt-d: Fix IQE handling to cover all descriptors in submission range

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

On 9/16/26 16:11, Guanghui Feng wrote:
> When an Invalidation Queue Error (IQE) occurs, hardware halts fetching
> and IQH points at the faulting descriptor. The previous code only
> checked whether IQH matched the first descriptor index of the current
> submission, missing faults on any other descriptor within the batch.
> 
> Expand the check to cover the entire submission range [index, wait_index],
> accounting for circular wrap-around.
> 
> Furthermore, after detecting IQE, the old recovery only replaced the
> single faulting slot with a copy of the wait descriptor and immediately
> returned -EINVAL. This left two problems:
> 
>    a) Hardware resumed fetching and could hit another invalid descriptor
>       in the same abandoned batch, raising a second IQE that no submitter
>       would claim — permanently deadlocking the queue.
> 
>    b) The caller reclaimed all batch slots (QI_FREE) while hardware might
>       still be asynchronously processing descriptors from that batch,
>       allowing concurrent overwrite and descriptor corruption.
> 
> Fix both by introducing qi_drain_remaining_descs(): upon IQE detection,
> overwrite the stranded slots in [IQH, wait_index) with fenced no-op wait
> descriptors, resubmit the wait descriptor at wait_index, clear IQE, and
> spin until hardware signals QI_DONE (with DMAR_OPERATION_TIMEOUT). This
> guarantees hardware has fully drained the batch before the caller
> reclaims slots.
> 

Fixes: 8a1d82462540 ("iommu/vt-d: Multiple descriptors per 
qi_submit_sync()")

> Signed-off-by: Guanghui Feng<guanghuifeng@linux.alibaba.com>
> ---
>   drivers/iommu/intel/dmar.c | 73 ++++++++++++++++++++++++++++++++------
>   1 file changed, 62 insertions(+), 11 deletions(-)

Queued for iommu/next. Thanks!