linux-kernel - RE: [PATCH] iommu: Add Kconfig help text for IOMMU

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Message-ID: <BN9PR11MB5276B168FF2BF15A4C55DEC48C769@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Tue, 9 May 2023 00:13:54 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "Torvalds, Linus" <torvalds@...ux-foundation.org>
CC:     Jason Gunthorpe <jgg@...dia.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Jean-Philippe Brucker" <jean-philippe@...aro.com>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>
Subject: RE: [PATCH] iommu: Add Kconfig help text for IOMMU_SVA

> From: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Sent: Tuesday, May 9, 2023 4:22 AM
>
> Leave the name MM_PASID aside, I am trying to capture the discussion with
> a
> patch below. I am struggling to get a clean solution since SVA code is
> common as you said "having a per-mm ASID for IO". Having x86 Kconfig
> select
> MM_PASID would be redundant if it is already selected by IOMMU_SVA.

Currently SVA relies on mm->pasid, w/ or w/o ENQCMD.

From this angle having IOMMU_SVA select MM_PASID looks sufficient to me.

If one day there is a reason to constrain mm->pasid only for ENQCMD, then
we can move to let arch config select MM_PASID.