[RFC PATCH v4] iommu/virtio: Use page size bitmap supported by endpoint

[Bharat Bhushan]

Different endpoint can support different page size, probe
endpoint if it supports specific page size otherwise use
global page sizes.

Signed-off-by: Bharat Bhushan <bbhushan2@xxxxxxxxxxx>
---
v3->v4:
 - Fix whitespace error

v2->v3:
 - Fixed error return for incompatible endpoint
 - __u64 changed to __le64 in header file

 drivers/iommu/virtio-iommu.c      | 53 +++++++++++++++++++++++++++----
 include/uapi/linux/virtio_iommu.h |  7 ++++
 2 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index cce329d71fba..ab09c04b1702 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -78,6 +78,7 @@ struct viommu_endpoint {
 	struct viommu_dev		*viommu;
 	struct viommu_domain		*vdomain;
 	struct list_head		resv_regions;
+	u64				pgsize_bitmap;
 };
 
 struct viommu_request {
@@ -415,6 +416,19 @@ static int viommu_replay_mappings(struct viommu_domain *vdomain)
 	return ret;
 }
 
+static int viommu_set_pgsize_bitmap(struct viommu_endpoint *vdev,
+				    struct virtio_iommu_probe_pgsize_mask *mask,
+				    size_t len)
+{
+	u64 pgsize_bitmap = le64_to_cpu(mask->pgsize_bitmap);
+
+	if (len < sizeof(*mask))
+		return -EINVAL;
+
+	vdev->pgsize_bitmap = pgsize_bitmap;
+	return 0;
+}
+
 static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
 			       struct virtio_iommu_probe_resv_mem *mem,
 			       size_t len)
@@ -499,6 +513,9 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
 		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
 			ret = viommu_add_resv_mem(vdev, (void *)prop, len);
 			break;
+		case VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK:
+			ret = viommu_set_pgsize_bitmap(vdev, (void *)prop, len);
+			break;
 		default:
 			dev_err(dev, "unknown viommu prop 0x%x\n", type);
 		}
@@ -607,16 +624,17 @@ static struct iommu_domain *viommu_domain_alloc(unsigned type)
 	return &vdomain->domain;
 }
 
-static int viommu_domain_finalise(struct viommu_dev *viommu,
+static int viommu_domain_finalise(struct viommu_endpoint *vdev,
 				  struct iommu_domain *domain)
 {
 	int ret;
 	struct viommu_domain *vdomain = to_viommu_domain(domain);
+	struct viommu_dev *viommu = vdev->viommu;
 
 	vdomain->viommu		= viommu;
 	vdomain->map_flags	= viommu->map_flags;
 
-	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
+	domain->pgsize_bitmap	= vdev->pgsize_bitmap;
 	domain->geometry	= viommu->geometry;
 
 	ret = ida_alloc_range(&viommu->domain_ids, viommu->first_domain,
@@ -642,6 +660,29 @@ static void viommu_domain_free(struct iommu_domain *domain)
 	kfree(vdomain);
 }
 
+/*
+ * Check whether the endpoint's capabilities are compatible with other
+ * endpoints in the domain. Report any inconsistency.
+ */
+static bool viommu_endpoint_is_compatible(struct viommu_endpoint *vdev,
+					  struct viommu_domain *vdomain)
+{
+	struct device *dev = vdev->dev;
+
+	if (vdomain->viommu != vdev->viommu) {
+		dev_err(dev, "cannot attach to foreign vIOMMU\n");
+		return false;
+	}
+
+	if (vdomain->domain.pgsize_bitmap != vdev->pgsize_bitmap) {
+		dev_err(dev, "incompatible domain bitmap 0x%lx != 0x%llx\n",
+			vdomain->domain.pgsize_bitmap, vdev->pgsize_bitmap);
+		return false;
+	}
+
+	return true;
+}
+
 static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
 {
 	int i;
@@ -657,10 +698,9 @@ static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
 		 * Properly initialize the domain now that we know which viommu
 		 * owns it.
 		 */
-		ret = viommu_domain_finalise(vdev->viommu, domain);
-	} else if (vdomain->viommu != vdev->viommu) {
-		dev_err(dev, "cannot attach to foreign vIOMMU\n");
-		ret = -EXDEV;
+		ret = viommu_domain_finalise(vdev, domain);
+	} else if (!viommu_endpoint_is_compatible(vdev, vdomain)) {
+		ret = -EINVAL;
 	}
 	mutex_unlock(&vdomain->mutex);
 
@@ -875,6 +915,7 @@ static int viommu_add_device(struct device *dev)
 
 	vdev->dev = dev;
 	vdev->viommu = viommu;
+	vdev->pgsize_bitmap = viommu->pgsize_bitmap;
 	INIT_LIST_HEAD(&vdev->resv_regions);
 	fwspec->iommu_priv = vdev;
 
diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h
index 237e36a280cb..bd0a1a844081 100644
--- a/include/uapi/linux/virtio_iommu.h
+++ b/include/uapi/linux/virtio_iommu.h
@@ -111,6 +111,7 @@ struct virtio_iommu_req_unmap {
 
 #define VIRTIO_IOMMU_PROBE_T_NONE		0
 #define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
+#define VIRTIO_IOMMU_PROBE_T_PAGE_SIZE_MASK	2
 
 #define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
 
@@ -119,6 +120,12 @@ struct virtio_iommu_probe_property {
 	__le16					length;
 };
 
+struct virtio_iommu_probe_pgsize_mask {
+	struct virtio_iommu_probe_property	head;
+	__u8					reserved[4];
+	__le64					pgsize_bitmap;
+};
+
 #define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
 #define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
 
-- 
2.17.1