linux-kernel - Re: [PATCH 1/4] iommu/vt-d: Implement set device pasid op for default domain

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Date:   Mon, 6 Mar 2023 11:04:43 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     Baolu Lu <baolu.lu@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        Jason Gunthorpe <jgg@...dia.com>,
        Joerg Roedel <joro@...tes.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>,
        "David Woodhouse" <dwmw2@...radead.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 1/4] iommu/vt-d: Implement set device pasid op for
 default domain

Hi Kevin,

On Fri, 3 Mar 2023 05:35:58 +0000, "Tian, Kevin" <kevin.tian@...el.com>
wrote:

> > From: Baolu Lu <baolu.lu@...ux.intel.com>
> > Sent: Friday, March 3, 2023 12:38 PM
> > 
> > On 3/3/23 11:02 AM, Tian, Kevin wrote:  
> > >> From: Baolu Lu <baolu.lu@...ux.intel.com>
> > >> Sent: Friday, March 3, 2023 10:49 AM
> > >>
> > >> On 3/3/23 10:36 AM, Tian, Kevin wrote:  
> > >>>> From: Baolu Lu <baolu.lu@...ux.intel.com>
> > >>>> Sent: Thursday, March 2, 2023 10:07 PM  
> > >>>>> +
> > >>>>> +	if (!sm_supported(iommu) || !info)  
> > >>>>
> > >>>> @info has been referenced. !info check makes no sense.
> > >>>>
> > >>>> Add pasid_supported(iommu).
> > >>>>
> > >>>> Do you need to check whether the domain is compatible for this rid
> > >>>> pasid?  
> > >>>
> > >>> what kind of compatibility is concerned here? In concept a pasid
> > >>> can be attached to any domain if it has been successfully attached
> > >>> to rid. Probably we can add a check here that RID2PASID must
> > >>> point to the domain already.  
> > >>
> > >> "...if it has been successfully attached to rid..."
> > >>
> > >> We should not have this assumption in iommu driver's callback. The  
> > iommu  
> > >> driver has no (and should not have) knowledge about the history of
> > >> any domain.  
> > >
> > > but this is an op for default domain which must have been attached
> > > to RID2PASID and any compatibility check between this domain and
> > > device should be passed.  
> > 
> > This is an op for DMA, DMA-FQ and UNMANAGED domain. The IOMMU
> > driver
> > doesn't need to interpret the default domain concept. :-)
> >   
> 
> yes if we target a general callback for all those domain types.
> 
> and probably this is the right thing to do as in the end DMA type will
> be removed with Jason's cleanup
so, let me recap. set_dev_pasid() should make no assumptions of
ordering, i.e. it is equal to iommu_domain_ops.attach_dev().
It will be kind of the same as Baolu's old patch
https://lore.kernel.org/linux-iommu/20220614034411.1634238-1-baolu.lu@linux.intel.com/


Thanks,

Jacob