Re: [PATCH v4 2/6] iommu: Add a helper to do PASID lookup from domain

[Jacob Pan]

Hi Baolu,

On Thu, 19 May 2022 14:41:06 +0800, Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
wrote:

> > IOMMU group maintains a PASID array which stores the associated IOMMU
> > domains. This patch introduces a helper function to do domain to PASID
> > look up. It will be used by TLB flush and device-PASID attach
> > verification.  
> 
> Do you really need this?
> 
> The IOMMU driver has maintained a device tracking list for each domain.
> It has been used for cache invalidation when unmap() is called against
> dma domain.
Yes, I am aware of the device list. In v3, I stored DMA API PASID in device
list of device_domain_info. Since we already have a pasid_array, Jason
suggested to share the storage with the code. This helper is needed to
reverse look up the DMA PASID based on the domain attached.
Discussions here:
https://lore.kernel.org/lkml/20220511170025.GF49344@xxxxxxxxxx/t/#mf7cb7d54d89e6e732a020dc22435260da0a49580

Thanks,

Jacob