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

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Message-Id: <20230506133134.1492395-1-jacob.jun.pan@linux.intel.com>
Date:   Sat,  6 May 2023 06:31:34 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Jason Gunthorpe <jgg@...dia.com>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Robin Murphy" <robin.murphy@....com>
Cc:     "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>,
        torvalds@...ux-foundation.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH] iommu: Add Kconfig help text for IOMMU_SVA

Shared Virtual Addressing (SVA) is not immediately intuitive to people
who work outside IOMMU subsystem, add some explanation to make it less
opaque.
Link: https://lore.kernel.org/lkml/ZE70doFi8X3KgfrV@ziepe.ca/t/#meaa938c91857665b376db59e16b532ba9d4ea013
Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
---
 drivers/iommu/Kconfig | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index db98c3f86e8c..0f7181007dc1 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -1,4 +1,4 @@
-# SPDX-License-Identifier: GPL-2.0-only
+# PDX-License-Identifier: GPL-2.0-only
 # The IOVA library may also be used by non-IOMMU_API users
 config IOMMU_IOVA
 	tristate
@@ -155,7 +155,14 @@ config IOMMU_DMA
 
 # Shared Virtual Addressing
 config IOMMU_SVA
-	bool
+	bool "Shared Virtual Addressing"
+	help
+	  IOMMU and CPU share page tables for user processes thus DMA can use
+	  CPU virtual address. Under intel architecture, it is also called
+	  Shared Virtual Memory (SVM).
+	  With SVA, DMA requests are tagged with PCIe Process Address Space ID
+	  (PASID) or Substream ID (ARM SMMU term) with which page tables are
+	  associated.
 
 config FSL_PAMU
 	bool "Freescale IOMMU support"
-- 
2.25.1