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

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Date:   Thu, 19 May 2022 13:10:37 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>, dmaengine@...r.kernel.org,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>, vkoul@...nel.org,
        robin.murphy@....com, will@...nel.org, Yi Liu <yi.l.liu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Eric Auger <eric.auger@...hat.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v4 2/6] iommu: Add a helper to do PASID lookup from
 domain

Hi Baolu,

On Thu, 19 May 2022 14:41:06 +0800, Baolu Lu <baolu.lu@...ux.intel.com>
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@nvidia.com/t/#mf7cb7d54d89e6e732a020dc22435260da0a49580

Thanks,

Jacob