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

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Message-ID: <ZFkpk8y8mUZuZjkV@nvidia.com>
Date:   Mon, 8 May 2023 13:55:47 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, 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>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>
Subject: Re: [PATCH] iommu: Add Kconfig help text for IOMMU_SVA

On Mon, May 08, 2023 at 09:42:18AM -0700, Linus Torvalds wrote:
> On Mon, May 8, 2023 at 9:35 AM Jacob Pan <jacob.jun.pan@...ux.intel.com> wrote:
> >
> > Conversely, we could also have some part of PASID that is not about SVA.
> 
> If that's the case, then we should *definitely* have that IOMMU_PASID
> kind of config option.
> 
> Then IOMMU_SVA - that needs PASID - can "select" it, but any other use
> - that doesn't bother about SVA but might want PASID for its own
> nefarious purposes - can also select it.

Yes, this has been unwinding slowly, but this mm part is about SVA,
and specifically ENQCMD, and not about PASID, other than SVA and
ENCQCMD are both using PASID.

CONFIG_IOMMU_MM_PASID perhaps? Says what it does without a clue about
why it does it. x86 arch code could select it ideally?

Jason