[PATCH v2 08/25] iommu: Allow an IDENTITY domain as the default_domain in ARM32

[Jason Gunthorpe <jgg@nvidia.com>]

Even though dma-iommu.c and CONFIG_ARM_DMA_USE_IOMMU do approximately the
same stuff, the way they relate to the IOMMU core is quiet different.

dma-iommu.c expects the core code to setup an UNMANAGED domain (of type
IOMMU_DOMAIN_DMA) and then configures itself to use that domain. This
becomes the default_domain for the group.

ARM_DMA_USE_IOMMU does not use the default_domain, instead it directly
allocates an UNMANAGED domain and operates it just like an external
driver. In this case group->default_domain is NULL.

If the driver provides a global static identity_domain then automatically
use it as the default_domain when in ARM_DMA_USE_IOMMU mode.

This allows drivers that implemented default_domain == NULL as an IDENTITY
translation to trivially get a properly labeled non-NULL default_domain on
ARM32 configs.

With this arrangment when ARM_DMA_USE_IOMMU wants to disconnect from the
device the normal detach_domain flow will restore the IDENTITY domain as
the default domain. Overall this makes attach_dev() of the IDENTITY domain
called in the same places as detach_dev().

This effectively migrates these drivers to default_domain mode. For
drivers that support ARM64 they will gain support for the IDENTITY
translation mode for the dma_api and behave in a uniform way.

Drivers use this by setting ops->identity_domain to a static singleton
iommu_domain that implements the identity attach. If the core detects
ARM_DMA_USE_IOMMU mode then it automatically attaches the IDENTITY domain
during probe.

Drivers can continue to prevent the use of DMA translation by returning
IOMMU_DOMAIN_IDENTITY from def_domain_type, this will completely prevent
IOMMU_DMA from running but will not impact ARM_DMA_USE_IOMMU.

This allows removing the set_platform_dma_ops() from every remaining
driver.

Remove the set_platform_dma_ops from rockchip and mkt_v1 as all it does
is set an existing global static identity domain. mkt_v1 does not support
IOMMU_DOMAIN_DMA and it does not compile on ARM64 so this transformation
is safe.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/iommu.c          | 40 +++++++++++++++++++++++++++++-----
 drivers/iommu/mtk_iommu_v1.c   | 12 ----------
 drivers/iommu/rockchip-iommu.c | 10 ---------
 3 files changed, 35 insertions(+), 27 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 8ba90571449cec..bed7cb6e5ee65b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1757,18 +1757,48 @@ static int iommu_get_default_domain_type(struct iommu_group *group,
 	int type;
 
 	lockdep_assert_held(&group->mutex);
+
+	/*
+	 * ARM32 drivers supporting CONFIG_ARM_DMA_USE_IOMMU can declare an
+	 * identity_domain and it will automatically become their default
+	 * domain. Later on ARM_DMA_USE_IOMMU will install its UNMANAGED domain.
+	 * Override the selection to IDENTITY if we are sure the driver supports
+	 * it.
+	 */
+	if (IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU) && ops->identity_domain) {
+		type = IOMMU_DOMAIN_IDENTITY;
+		if (best_type && type && best_type != type)
+			goto err;
+		best_type = target_type = IOMMU_DOMAIN_IDENTITY;
+	}
+
 	for_each_group_device(group, gdev) {
 		type = best_type;
 		if (ops->def_domain_type) {
 			type = ops->def_domain_type(gdev->dev);
-			if (best_type && type && best_type != type)
+			if (best_type && type && best_type != type) {
+				/* Stick with the last driver override we saw */
+				best_type = type;
 				goto err;
+			}
 		}
 
 		if (dev_is_pci(gdev->dev) && to_pci_dev(gdev->dev)->untrusted) {
-			type = IOMMU_DOMAIN_DMA;
-			if (best_type && type && best_type != type)
-				goto err;
+			/*
+			 * We don't have any way for the iommu core code to
+			 * force arm_iommu to activate so we can't enforce
+			 * trusted. Log it and keep going with the IDENTITY
+			 * default domain.
+			 */
+			if (IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)) {
+				dev_warn(
+					gdev->dev,
+					"PCI device is untrusted but ARM32 does not support secure IOMMU operation, continuing anyway.\n");
+			} else {
+				type = IOMMU_DOMAIN_DMA;
+				if (best_type && type && best_type != type)
+					goto err;
+			}
 		}
 		best_type = type;
 		last_dev = gdev->dev;
@@ -1790,7 +1820,7 @@ static int iommu_get_default_domain_type(struct iommu_group *group,
 		"Device needs domain type %s, but device %s in the same iommu group requires type %s - using default\n",
 		iommu_domain_type_str(type), dev_name(last_dev),
 		iommu_domain_type_str(best_type));
-	return 0;
+	return best_type;
 }
 
 static void iommu_group_do_probe_finalize(struct device *dev)
diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index cc3e7d53d33ad9..7c0c1d50df5f75 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -337,11 +337,6 @@ static struct iommu_domain mtk_iommu_v1_identity_domain = {
 	.ops = &mtk_iommu_v1_identity_ops,
 };
 
-static void mtk_iommu_v1_set_platform_dma(struct device *dev)
-{
-	mtk_iommu_v1_identity_attach(&mtk_iommu_v1_identity_domain, dev);
-}
-
 static int mtk_iommu_v1_map(struct iommu_domain *domain, unsigned long iova,
 			    phys_addr_t paddr, size_t pgsize, size_t pgcount,
 			    int prot, gfp_t gfp, size_t *mapped)
@@ -457,11 +452,6 @@ static int mtk_iommu_v1_create_mapping(struct device *dev, struct of_phandle_arg
 	return 0;
 }
 
-static int mtk_iommu_v1_def_domain_type(struct device *dev)
-{
-	return IOMMU_DOMAIN_IDENTITY;
-}
-
 static struct iommu_device *mtk_iommu_v1_probe_device(struct device *dev)
 {
 	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
@@ -599,10 +589,8 @@ static const struct iommu_ops mtk_iommu_v1_ops = {
 	.probe_device	= mtk_iommu_v1_probe_device,
 	.probe_finalize = mtk_iommu_v1_probe_finalize,
 	.release_device	= mtk_iommu_v1_release_device,
-	.def_domain_type = mtk_iommu_v1_def_domain_type,
 	.device_group	= generic_device_group,
 	.pgsize_bitmap	= MT2701_IOMMU_PAGE_SIZE,
-	.set_platform_dma_ops = mtk_iommu_v1_set_platform_dma,
 	.owner          = THIS_MODULE,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
 		.attach_dev	= mtk_iommu_v1_attach_device,
diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index ebce56d6e9c634..9e1296a856ac4c 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -1026,13 +1026,6 @@ static struct iommu_domain rk_identity_domain = {
 	.ops = &rk_identity_ops,
 };
 
-#ifdef CONFIG_ARM
-static void rk_iommu_set_platform_dma(struct device *dev)
-{
-	WARN_ON(rk_iommu_identity_attach(&rk_identity_domain, dev));
-}
-#endif
-
 static int rk_iommu_attach_device(struct iommu_domain *domain,
 		struct device *dev)
 {
@@ -1211,9 +1204,6 @@ static const struct iommu_ops rk_iommu_ops = {
 	.probe_device = rk_iommu_probe_device,
 	.release_device = rk_iommu_release_device,
 	.device_group = rk_iommu_device_group,
-#ifdef CONFIG_ARM
-	.set_platform_dma_ops = rk_iommu_set_platform_dma,
-#endif
 	.pgsize_bitmap = RK_IOMMU_PGSIZE_BITMAP,
 	.of_xlate = rk_iommu_of_xlate,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
-- 
2.40.1