linux-kernel - [RFC PATCH 4/4] iommu: Determine default domain type before allocating domain

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Date:   Wed,  1 Jan 2020 13:26:48 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     ashok.raj@...el.com, jacob.jun.pan@...el.com, kevin.tian@...el.com,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [RFC PATCH 4/4] iommu: Determine default domain type before allocating domain

Determine the default domain type for each group and use it to
allocate the iommu domain.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/iommu.c | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 716326a2ee5b..fc1df1acbd25 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -43,6 +43,7 @@ struct iommu_group {
 	int id;
 	struct iommu_domain *default_domain;
 	struct iommu_domain *domain;
+	unsigned int def_domain_type;
 };
 
 struct group_device {
@@ -1383,6 +1384,33 @@ static int alloc_iommu_group(struct device *dev, void *data)
 	return 0;
 }
 
+static void get_group_def_domain_type(struct iommu_group *group)
+{
+	struct group_device *tmp = NULL;
+
+	mutex_lock(&group->mutex);
+	list_for_each_entry(tmp, &group->devices, list) {
+		struct device *dev = tmp->dev;
+
+		/*
+		 * If there are any untrusted devices in the group, force
+		 * IOMMU_DOMAIN_DMA to prevent DMA attack from malicious
+		 * devices.
+		 */
+		if (dev_is_pci(dev) && to_pci_dev(dev)->untrusted) {
+			group->def_domain_type = IOMMU_DOMAIN_DMA;
+			break;
+		}
+
+		if (dev->iommu_passthrough)
+			group->def_domain_type = IOMMU_DOMAIN_IDENTITY;
+	}
+	mutex_unlock(&group->mutex);
+
+	if (!group->def_domain_type)
+		group->def_domain_type = iommu_def_domain_type;
+}
+
 /**
  * iommu_group_get_for_dev - Find or create the IOMMU group for a device
  * @dev: target device
@@ -1412,13 +1440,14 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev)
 	if (!group->default_domain) {
 		struct iommu_domain *dom;
 
-		dom = __iommu_domain_alloc(dev->bus, iommu_def_domain_type);
-		if (!dom && iommu_def_domain_type != IOMMU_DOMAIN_DMA) {
+		get_group_def_domain_type(group);
+		dom = __iommu_domain_alloc(dev->bus, group->def_domain_type);
+		if (!dom && group->def_domain_type != IOMMU_DOMAIN_DMA) {
 			dom = __iommu_domain_alloc(dev->bus, IOMMU_DOMAIN_DMA);
 			if (dom) {
 				dev_warn(dev,
 					 "failed to allocate default IOMMU domain of type %u; falling back to IOMMU_DOMAIN_DMA",
-					 iommu_def_domain_type);
+					 group->def_domain_type);
 			}
 		}
 
-- 
2.17.1