linux-kernel - Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs

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Message-ID: <YFxlaGyJkTM1m9IX@myrica>
Date:   Thu, 25 Mar 2021 11:26:48 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     Jason Gunthorpe <jgg@...dia.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        iommu@...ts.linux-foundation.org, cgroups@...r.kernel.org,
        Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        Wu Hao <hao.wu@...el.com>, Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and
 allocation APIs

On Wed, Mar 24, 2021 at 10:02:46AM -0700, Jacob Pan wrote:
> > And a flag IOMMU_SVA_BIND_SUPERVISOR (not that I plan to implement it in
> > the SMMU, but I think we need to clean the current usage)
> > 
> You mean move #define SVM_FLAG_SUPERVISOR_MODE out of Intel code to be a
> generic flag in iommu-sva-lib.h called IOMMU_SVA_BIND_SUPERVISOR?

Yes, though it would need to be in iommu.h since it's used by device
drivers

> > Also wondering about device driver allocating auxiliary domains for their
> > private use, to do iommu_map/unmap on private PASIDs (a clean replacement
> > to super SVA, for example). Would that go through the same path as
> > /dev/ioasid and use the cgroup of current task?
> >
> For the in-kernel private use, I don't think we should restrict based on
> cgroup, since there is no affinity to user processes. I also think the
> PASID allocation should just use kernel API instead of /dev/ioasid. Why
> would user space need to know the actual PASID # for device private domains?
> Maybe I missed your idea?

No that's my bad, I didn't get the role of /dev/ioasid. Let me give the
series a proper read.

Thanks,
Jean