> On Mar 16, 2021, at 8:16 PM, Longpeng (Mike, Cloud Infrastructure Service Product Dept.) <longpeng2@huawei.com> wrote:
> 
> Hi guys,
> 
> We find the Intel iommu cache (i.e. iotlb) maybe works wrong in a special
> situation, it would cause DMA fails or get wrong data.
> 
> The reproducer (based on Alex's vfio testsuite[1]) is in attachment, it can
> reproduce the problem with high probability (~50%).

I saw Lu replied, and he is much more knowledgable than I am (I was just
intrigued by your email).

However, if I were you I would try also to remove some “optimizations” to
look for the root-cause (e.g., use domain specific invalidations instead
of page-specific).

The first thing that comes to my mind is the invalidation hint (ih) in
iommu_flush_iotlb_psi(). I would remove it to see whether you get the
failure without it.