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Date:   Fri, 16 Sep 2022 11:05:47 +0800
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Cc:     baolu.lu@linux.intel.com, Joerg Roedel <joro@8bytes.org>,
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To:     Ethan Zhao <haifeng.zhao@linux.intel.com>, iommu@lists.linux.dev
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From:   Baolu Lu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH 1/1] iommu/vt-d: Enable PASID during iommu device probe
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On 2022/9/16 10:40, Ethan Zhao wrote:
>>
>> I may not get you exactly. ???? Some IOMMU features reply on PASID
>> capabilities on both IOMMU and device. The IOMMU drivers enumerate the
>> capabilities and enable them if they are supported.
> I might not express it straightforward,  I mean with this patch iommu 
> deals with
> 
> the complexity of enabling PASID (globally?)  or not at probing stage , 
> instead
> 
> of other device driver side decision to request IOMMU PASID enabling during
> 
> their setup state.  if so you move the decision to iommu probe stage. 
> hmmm...

I am sorry that the commit message was a bit confusing. Actually we
always enable PASID at iommu probe path w/ or w/o this patch.

> 
> Pros,  iommu driver controls everything about PASID enabling.
> 
> Cons,  iommu driver handles all possible complexity about capability 
> matching

Do device drivers need to configure PCI PASID without IOMMU? I searched
the tree and found nothing.

Best regards,
baolu