[PATCH v3 07/10] iommu/vt-d: Keep swiotlb on if bounce page is necessary

[Lu Baolu <baolu.lu@linux.intel.com>]

The bouce page is necessary whenever there are untrusted
devices in the system. The bounce page policy depends on
swiotlb, hence don't turn off swiotlb if untrusted devices
exist.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Mika Westerberg <mika.westerberg@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 drivers/iommu/intel-iommu.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index af040602bd44..e4a164324bdd 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4528,22 +4528,27 @@ const struct attribute_group *intel_iommu_groups[] = {
 	NULL,
 };
 
-static int __init platform_optin_force_iommu(void)
+static inline bool platform_has_untrusted_device(void)
 {
+	bool has_untrusted_device = false;
 	struct pci_dev *pdev = NULL;
-	bool has_untrusted_dev = false;
-
-	if (!dmar_platform_optin() || no_platform_optin)
-		return 0;
 
 	for_each_pci_dev(pdev) {
 		if (pdev->untrusted) {
-			has_untrusted_dev = true;
+			has_untrusted_device = true;
 			break;
 		}
 	}
 
-	if (!has_untrusted_dev)
+	return has_untrusted_device;
+}
+
+static int __init platform_optin_force_iommu(void)
+{
+	if (!dmar_platform_optin() || no_platform_optin)
+		return 0;
+
+	if (!platform_has_untrusted_device())
 		return 0;
 
 	if (no_iommu || dmar_disabled)
@@ -4557,9 +4562,6 @@ static int __init platform_optin_force_iommu(void)
 		iommu_identity_mapping |= IDENTMAP_ALL;
 
 	dmar_disabled = 0;
-#if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
-	swiotlb = 0;
-#endif
 	no_iommu = 0;
 
 	return 1;
@@ -4653,7 +4655,8 @@ int __init intel_iommu_init(void)
 	up_write(&dmar_global_lock);
 
 #if defined(CONFIG_X86) && defined(CONFIG_SWIOTLB)
-	swiotlb = 0;
+	if (!platform_has_untrusted_device())
+		swiotlb = 0;
 #endif
 	dma_ops = &intel_dma_ops;
 
-- 
2.17.1