linux-kernel - Re: [PATCH v2 6/8] iommu/vt-d: Implement set_dev

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Message-ID: <20230328084015.5c8c08ca@jacob-builder>
Date:   Tue, 28 Mar 2023 08:40:15 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        Jason Gunthorpe <jgg@...dia.com>,
        Lu Baolu <baolu.lu@...ux.intel.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 v2 6/8] iommu/vt-d: Implement set_dev_pasid domain op

Hi Kevin,

On Tue, 28 Mar 2023 07:47:45 +0000, "Tian, Kevin" <kevin.tian@...el.com>
wrote:

> > From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> > Sent: Tuesday, March 28, 2023 7:22 AM
> > 
> > Devices that use ENQCMDS to submit work on buffers mapped by DMA API
> > must attach a PASID to the default domain of the device. In preparation
> > for this use case, this patch implements set_dev_pasid() for the
> > default_domain_ops. Besides PASID attachment, device will also be
> > attached to the domain as the result of this call if the device has not
> > been attached before.
> >   
> 
> I didn't get the last point. PASID attach should only have the scope
> for the pasid. RID of the device might be attached to another domain
> which shouldn't be changed by this call.
I meant if the RID context has not been set up before attaching this PASID,
this call will also set up the context, PASID dir etc. In the end, we
eliminated ordering requirement of attaching device, RID_PASID first, then
other PASIDs.
How about:
"If the device context has not been set up prior to this call, this will
set up the device context in addition to PASID attachment."

Thanks,

Jacob