diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 6f07f3b21816..15b831113ded 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -359,6 +359,31 @@ config ARM_SMMU
 	  Say Y here if your SoC includes an IOMMU device implementing
 	  the ARM SMMU architecture.
 
+config ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT
+	bool "Default to disabling bypass on ARM SMMU v1 and v2"
+	depends on ARM_SMMU
+	default y
+	help
+	  Say Y here to (by default) disable bypass streams such that
+	  incoming transactions from devices that are not attached to
+	  an iommu domain will report an abort back to the device and
+	  will not be allowed to pass through the SMMU.
+
+	  Any old kernels that existed before this KConfig was
+	  introduced would default to _allowing_ bypass (AKA the
+	  equivalent of NO for this config).  However the default for
+	  this option is YES because the old behavior is insecure.
+
+	  There are few reasons to allow unmatched stream bypass, and
+	  even fewer good ones.  If saying YES here breaks your board
+	  you should work on fixing your board.  This KConfig option
+	  is expected to be removed in the future and we'll simply
+	  hardcode the bypass disable in the code.
+
+	  NOTE: the kernel command line parameter
+	  'arm-smmu.disable_bypass' will continue to override this
+	  config.
+
 config ARM_SMMU_V3
 	bool "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
 	depends on ARM64
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 045d93884164..930c07635956 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -110,7 +110,8 @@ static int force_stage;
 module_param(force_stage, int, S_IRUGO);
 MODULE_PARM_DESC(force_stage,
 	"Force SMMU mappings to be installed at a particular stage of translation. A value of '1' or '2' forces the corresponding stage. All other values are ignored (i.e. no stage is forced). Note that selecting a specific stage will disable support for nested translation.");
-static bool disable_bypass;
+static bool disable_bypass =
+	IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT);
 module_param(disable_bypass, bool, S_IRUGO);
 MODULE_PARM_DESC(disable_bypass,
 	"Disable bypass streams such that incoming transactions from devices that are not attached to an iommu domain will report an abort back to the device and will not be allowed to pass through the SMMU.");