linux-kernel - [PATCH v5 3/5] iommu: Allow iommu_change_dev_def_domain() realloc same default domain type

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Date:   Tue, 15 Feb 2022 01:29:04 +0800
From:   John Garry <john.garry@...wei.com>
To:     <joro@...tes.org>, <will@...nel.org>, <robin.murphy@....com>
CC:     <mst@...hat.com>, <jasowang@...hat.com>,
        <baolu.lu@...ux.intel.com>, <iommu@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>,
        <virtualization@...ts.linux-foundation.org>, <hch@....de>,
        <chenxiang66@...ilicon.com>, <linuxarm@...wei.com>,
        John Garry <john.garry@...wei.com>
Subject: [PATCH v5 3/5] iommu: Allow iommu_change_dev_def_domain() realloc same default domain type

Allow iommu_change_dev_def_domain() to create a new default domain, keeping
the same as current.

Also remove comment about the function purpose, which will become stale.

Signed-off-by: John Garry <john.garry@...wei.com>
---
 drivers/iommu/iommu.c | 49 ++++++++++++++++++++++---------------------
 include/linux/iommu.h |  1 +
 2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 5e7ed969b870..df9ffd76c184 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3124,6 +3124,7 @@ u32 iommu_sva_get_pasid(struct iommu_sva *handle)
 }
 EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
 
+
 /*
  * Changes the default domain of an iommu group that has *only* one device
  *
@@ -3134,10 +3135,6 @@ EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
  *
  * Returns 0 on success and error code on failure
  *
- * Note:
- * 1. Presently, this function is called only when user requests to change the
- *    group's default domain type through /sys/kernel/iommu_groups/<grp_id>/type
- *    Please take a closer look if intended to use for other purposes.
  */
 static int iommu_change_dev_def_domain(struct iommu_group *group,
 				       struct device *prev_dev, int type)
@@ -3190,28 +3187,32 @@ static int iommu_change_dev_def_domain(struct iommu_group *group,
 		goto out;
 	}
 
-	dev_def_dom = iommu_get_def_domain_type(dev);
-	if (!type) {
+	if (type == __IOMMU_DOMAIN_SAME) {
+		type = prev_dom->type;
+	} else {
+		dev_def_dom = iommu_get_def_domain_type(dev);
+		if (!type) {
+			/*
+			 * If the user hasn't requested any specific type of domain and
+			 * if the device supports both the domains, then default to the
+			 * domain the device was booted with
+			 */
+			type = dev_def_dom ? : iommu_def_domain_type;
+		} else if (dev_def_dom && type != dev_def_dom) {
+			dev_err_ratelimited(prev_dev, "Device cannot be in %s domain\n",
+					    iommu_domain_type_str(type));
+			ret = -EINVAL;
+			goto out;
+		}
+
 		/*
-		 * If the user hasn't requested any specific type of domain and
-		 * if the device supports both the domains, then default to the
-		 * domain the device was booted with
+		 * Switch to a new domain only if the requested domain type is different
+		 * from the existing default domain type
 		 */
-		type = dev_def_dom ? : iommu_def_domain_type;
-	} else if (dev_def_dom && type != dev_def_dom) {
-		dev_err_ratelimited(prev_dev, "Device cannot be in %s domain\n",
-				    iommu_domain_type_str(type));
-		ret = -EINVAL;
-		goto out;
-	}
-
-	/*
-	 * Switch to a new domain only if the requested domain type is different
-	 * from the existing default domain type
-	 */
-	if (prev_dom->type == type) {
-		ret = 0;
-		goto out;
+		if (prev_dom->type == type) {
+			ret = 0;
+			goto out;
+		}
 	}
 
 	/* We can bring up a flush queue without tearing down the domain */
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index de0c57a567c8..d242fccc7c2d 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -62,6 +62,7 @@ struct iommu_domain_geometry {
 					      implementation              */
 #define __IOMMU_DOMAIN_PT	(1U << 2)  /* Domain is identity mapped   */
 #define __IOMMU_DOMAIN_DMA_FQ	(1U << 3)  /* DMA-API uses flush queue    */
+#define __IOMMU_DOMAIN_SAME	(1U << 4)  /* Keep same type (internal)   */
 
 /*
  * This are the possible domain-types
-- 
2.26.2