[RFC PATCH v2 2/5] iommu/virtio-iommu: Add probe request

[Jean-Philippe Brucker <jean-philippe.brucker@arm.com>]

When the device offers the probe feature, send a probe request for each
device managed by the IOMMU. Extract RESV_MEM information. When we
encounter a MSI doorbell region, set it up as a IOMMU_RESV_MSI region.
This will tell other subsystems that there is no need to map the MSI
doorbell in the virtio-iommu, because MSIs bypass it.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
---
 drivers/iommu/virtio-iommu.c      | 165 ++++++++++++++++++++++++++++++++++++--
 include/uapi/linux/virtio_iommu.h |  37 +++++++++
 2 files changed, 195 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index feb8c8925c3a..79e0add94e05 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -45,6 +45,7 @@ struct viommu_dev {
 	struct iommu_domain_geometry	geometry;
 	u64				pgsize_bitmap;
 	u8				domain_bits;
+	u32				probe_size;
 };
 
 struct viommu_mapping {
@@ -72,6 +73,7 @@ struct viommu_domain {
 struct viommu_endpoint {
 	struct viommu_dev		*viommu;
 	struct viommu_domain		*vdomain;
+	struct list_head		resv_regions;
 };
 
 struct viommu_request {
@@ -139,6 +141,10 @@ static int viommu_get_req_size(struct viommu_dev *viommu,
 	case VIRTIO_IOMMU_T_UNMAP:
 		size = sizeof(r->unmap);
 		break;
+	case VIRTIO_IOMMU_T_PROBE:
+		*bottom += viommu->probe_size;
+		size = sizeof(r->probe) + *bottom;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -448,6 +454,106 @@ static int viommu_replay_mappings(struct viommu_domain *vdomain)
 	return ret;
 }
 
+static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
+			       struct virtio_iommu_probe_resv_mem *mem,
+			       size_t len)
+{
+	struct iommu_resv_region *region = NULL;
+	unsigned long prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
+
+	u64 addr = le64_to_cpu(mem->addr);
+	u64 size = le64_to_cpu(mem->size);
+
+	if (len < sizeof(*mem))
+		return -EINVAL;
+
+	switch (mem->subtype) {
+	case VIRTIO_IOMMU_RESV_MEM_T_MSI:
+		region = iommu_alloc_resv_region(addr, size, prot,
+						 IOMMU_RESV_MSI);
+		break;
+	case VIRTIO_IOMMU_RESV_MEM_T_RESERVED:
+	default:
+		region = iommu_alloc_resv_region(addr, size, 0,
+						 IOMMU_RESV_RESERVED);
+		break;
+	}
+
+	list_add(&vdev->resv_regions, &region->list);
+
+	if (mem->subtype != VIRTIO_IOMMU_RESV_MEM_T_RESERVED &&
+	    mem->subtype != VIRTIO_IOMMU_RESV_MEM_T_MSI) {
+		/* Please update your driver. */
+		pr_warn("unknown resv mem subtype 0x%x\n", mem->subtype);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
+{
+	int ret;
+	u16 type, len;
+	size_t cur = 0;
+	struct virtio_iommu_req_probe *probe;
+	struct virtio_iommu_probe_property *prop;
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+	struct viommu_endpoint *vdev = fwspec->iommu_priv;
+
+	if (!fwspec->num_ids)
+		/* Trouble ahead. */
+		return -EINVAL;
+
+	probe = kzalloc(sizeof(*probe) + viommu->probe_size +
+			sizeof(struct virtio_iommu_req_tail), GFP_KERNEL);
+	if (!probe)
+		return -ENOMEM;
+
+	probe->head.type = VIRTIO_IOMMU_T_PROBE;
+	/*
+	 * For now, assume that properties of an endpoint that outputs multiple
+	 * IDs are consistent. Only probe the first one.
+	 */
+	probe->endpoint = cpu_to_le32(fwspec->ids[0]);
+
+	ret = viommu_send_req_sync(viommu, probe);
+	if (ret) {
+		kfree(probe);
+		return ret;
+	}
+
+	prop = (void *)probe->properties;
+	type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
+
+	while (type != VIRTIO_IOMMU_PROBE_T_NONE &&
+	       cur < viommu->probe_size) {
+		len = le16_to_cpu(prop->length);
+
+		switch (type) {
+		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
+			ret = viommu_add_resv_mem(vdev, (void *)prop->value, len);
+			break;
+		default:
+			dev_dbg(dev, "unknown viommu prop 0x%x\n", type);
+		}
+
+		if (ret)
+			dev_err(dev, "failed to parse viommu prop 0x%x\n", type);
+
+		cur += sizeof(*prop) + len;
+		if (cur >= viommu->probe_size)
+			break;
+
+		prop = (void *)probe->properties + cur;
+		type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
+	}
+
+	kfree(probe);
+
+	return 0;
+}
+
 /* IOMMU API */
 
 static bool viommu_capable(enum iommu_cap cap)
@@ -706,6 +812,7 @@ static struct viommu_dev *viommu_get_by_fwnode(struct fwnode_handle *fwnode)
 
 static int viommu_add_device(struct device *dev)
 {
+	int ret;
 	struct iommu_group *group;
 	struct viommu_endpoint *vdev;
 	struct viommu_dev *viommu = NULL;
@@ -723,8 +830,16 @@ static int viommu_add_device(struct device *dev)
 		return -ENOMEM;
 
 	vdev->viommu = viommu;
+	INIT_LIST_HEAD(&vdev->resv_regions);
 	fwspec->iommu_priv = vdev;
 
+	if (viommu->probe_size) {
+		/* Get additional information for this endpoint */
+		ret = viommu_probe_endpoint(viommu, dev);
+		if (ret)
+			return ret;
+	}
+
 	/*
 	 * Last step creates a default domain and attaches to it. Everything
 	 * must be ready.
@@ -738,7 +853,19 @@ static int viommu_add_device(struct device *dev)
 
 static void viommu_remove_device(struct device *dev)
 {
-	kfree(dev->iommu_fwspec->iommu_priv);
+	struct viommu_endpoint *vdev;
+	struct iommu_resv_region *entry, *next;
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+
+	if (!fwspec || fwspec->ops != &viommu_ops)
+		return;
+
+	vdev = fwspec->iommu_priv;
+
+	list_for_each_entry_safe(entry, next, &vdev->resv_regions, list)
+		kfree(entry);
+
+	kfree(vdev);
 }
 
 static struct iommu_group *viommu_device_group(struct device *dev)
@@ -756,15 +883,34 @@ static int viommu_of_xlate(struct device *dev, struct of_phandle_args *args)
 
 static void viommu_get_resv_regions(struct device *dev, struct list_head *head)
 {
-	struct iommu_resv_region *region;
+	struct iommu_resv_region *entry, *new_entry, *msi = NULL;
+	struct viommu_endpoint *vdev = dev->iommu_fwspec->iommu_priv;
 	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
 
-	region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, prot,
-					 IOMMU_RESV_SW_MSI);
-	if (!region)
-		return;
+	list_for_each_entry(entry, &vdev->resv_regions, list) {
+		/*
+		 * If the device registered a bypass MSI windows, use it.
+		 * Otherwise add a software-mapped region
+		 */
+		if (entry->type == IOMMU_RESV_MSI)
+			msi = entry;
+
+		new_entry = kmemdup(entry, sizeof(*entry), GFP_KERNEL);
+		if (!new_entry)
+			return;
+		list_add_tail(&new_entry->list, head);
+	}
 
-	list_add_tail(&region->list, head);
+	if (!msi) {
+		msi = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH,
+					      prot, IOMMU_RESV_SW_MSI);
+		if (!msi)
+			return;
+
+		list_add_tail(&msi->list, head);
+	}
+
+	iommu_dma_get_resv_regions(dev, head);
 }
 
 static void viommu_put_resv_regions(struct device *dev, struct list_head *head)
@@ -854,6 +1000,10 @@ static int viommu_probe(struct virtio_device *vdev)
 			     struct virtio_iommu_config, domain_bits,
 			     &viommu->domain_bits);
 
+	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_PROBE,
+			     struct virtio_iommu_config, probe_size,
+			     &viommu->probe_size);
+
 	viommu->geometry = (struct iommu_domain_geometry) {
 		.aperture_start	= input_start,
 		.aperture_end	= input_end,
@@ -931,6 +1081,7 @@ static unsigned int features[] = {
 	VIRTIO_IOMMU_F_MAP_UNMAP,
 	VIRTIO_IOMMU_F_DOMAIN_BITS,
 	VIRTIO_IOMMU_F_INPUT_RANGE,
+	VIRTIO_IOMMU_F_PROBE,
 };
 
 static struct virtio_device_id id_table[] = {
diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h
index 2b4cd2042897..eec90a2ab547 100644
--- a/include/uapi/linux/virtio_iommu.h
+++ b/include/uapi/linux/virtio_iommu.h
@@ -38,6 +38,7 @@
 #define VIRTIO_IOMMU_F_DOMAIN_BITS		1
 #define VIRTIO_IOMMU_F_MAP_UNMAP		2
 #define VIRTIO_IOMMU_F_BYPASS			3
+#define VIRTIO_IOMMU_F_PROBE			4
 
 struct virtio_iommu_config {
 	/* Supported page sizes */
@@ -49,6 +50,9 @@ struct virtio_iommu_config {
 	} input_range;
 	/* Max domain ID size */
 	__u8 					domain_bits;
+	__u8					padding[3];
+	/* Probe buffer size */
+	__u32					probe_size;
 } __packed;
 
 /* Request types */
@@ -56,6 +60,7 @@ struct virtio_iommu_config {
 #define VIRTIO_IOMMU_T_DETACH			0x02
 #define VIRTIO_IOMMU_T_MAP			0x03
 #define VIRTIO_IOMMU_T_UNMAP			0x04
+#define VIRTIO_IOMMU_T_PROBE			0x05
 
 /* Status types */
 #define VIRTIO_IOMMU_S_OK			0x00
@@ -128,6 +133,37 @@ struct virtio_iommu_req_unmap {
 	struct virtio_iommu_req_tail		tail;
 } __packed;
 
+#define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
+#define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
+
+struct virtio_iommu_probe_resv_mem {
+	__u8					subtype;
+	__u8					reserved[3];
+	__le64					addr;
+	__le64					size;
+} __packed;
+
+#define VIRTIO_IOMMU_PROBE_T_NONE		0
+#define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
+
+#define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
+
+struct virtio_iommu_probe_property {
+	__le16					type;
+	__le16					length;
+	__u8					value[];
+} __packed;
+
+struct virtio_iommu_req_probe {
+	struct virtio_iommu_req_head		head;
+	__le32					endpoint;
+	__u8					reserved[64];
+
+	__u8					properties[];
+
+	/* Tail follows the variable-length properties array (no padding) */
+} __packed;
+
 union virtio_iommu_req {
 	struct virtio_iommu_req_head		head;
 
@@ -135,6 +171,7 @@ union virtio_iommu_req {
 	struct virtio_iommu_req_detach		detach;
 	struct virtio_iommu_req_map		map;
 	struct virtio_iommu_req_unmap		unmap;
+	struct virtio_iommu_req_probe		probe;
 };
 
 #endif
-- 
2.14.3