Re: [PATCH] iommu: Add Kconfig help text for IOMMU_SVA

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	iommu@lists.linux.dev, Jason Gunthorpe <jgg@nvidia.com>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	Joerg Roedel <joro@8bytes.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Will Deacon <will@kernel.org>, Raj Ashok <ashok.raj@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>, Yi Liu <yi.l.liu@intel.com>,
	"Yu, Fenghua" <fenghua.yu@intel.com>
Subject: Re: [PATCH] iommu: Add Kconfig help text for IOMMU_SVA
Date: Sat, 6 May 2023 08:43:08 -0700	[thread overview]
Message-ID: <CAHk-=wgUiAtiszwseM1p2fCJ+sC4XWQ+YN4TanFhUgvUqjr9Xw@mail.gmail.com> (raw)
In-Reply-To: <20230506133134.1492395-1-jacob.jun.pan@linux.intel.com>

On Sat, May 6, 2023 at 6:27 AM Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:
>
> Shared Virtual Addressing (SVA) is not immediately intuitive to people
> who work outside IOMMU subsystem, add some explanation to make it less
> opaque.

So the patch has at least two problems.

The first is that you corrupted the SPDX line.

But the second is that the change from

-       bool
+       bool "Shared Virtual Addressing"

means that now Kconfig *asks* about this thing, which was never the
intent. The other Kconfig options that need it all do a

        select IOMMU_SVA

to get it picked.

I suspect that's why it then causes errors - because now the test
robot can enable the option even in situations where it makes no sense
and doesn't work.

So no, it's not that the option needs a help entry that can be queried
at Kconfig time. It's that the option needs a name that makes sense
and isn't some random jumble of letters that is only understandable to
people who already know exactly what it is.

               Linus