iommu: Bind process address spaces to devices

Add bind() and unbind() operations to the IOMMU API.
iommu_sva_bind_device() binds a device to an mm, and returns a handle to
the bond, which is released by calling iommu_sva_unbind_device().

Each mm bound to devices gets a PASID (by convention, a 20-bit system-wide
ID representing the address space), which can be retrieved with
iommu_sva_get_pasid(). When programming DMA addresses, device drivers
include this PASID in a device-specific manner, to let the device access
the given address space. Since the process memory may be paged out, device
and IOMMU must support I/O page faults (e.g. PCI PRI).

Using iommu_sva_set_ops(), device drivers provide an mm_exit() callback
that is called by the IOMMU driver if the process exits before the device
driver called unbind(). In mm_exit(), device driver should disable DMA
from the given context, so that the core IOMMU can reallocate the PASID.
Whether the process exited or nor, the device driver should always release
the handle with unbind().

To use these functions, device driver must first enable the
IOMMU_DEV_FEAT_SVA device feature with iommu_dev_enable_feature().

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 104 insertions, 0 deletions

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 344e27e8f188..f8fe112e507a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2135,3 +2135,107 @@ int iommu_aux_get_pasid(struct iommu_domain *domain, struct device *dev)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(iommu_aux_get_pasid);
+
+/**
+ * iommu_sva_bind_device() - Bind a process address space to a device
+ * @dev: the device
+ * @mm: the mm to bind, caller must hold a reference to it
+ *
+ * Create a bond between device and address space, allowing the device to access
+ * the mm using the returned PASID. If a bond already exists between @device and
+ * @mm, it is returned and an additional reference is taken. Caller must call
+ * iommu_sva_unbind_device() to release each reference.
+ *
+ * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
+ * initialize the required SVA features.
+ *
+ * On error, returns an ERR_PTR value.
+ */
+struct iommu_sva *
+iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
+{
+	struct iommu_group *group;
+	struct iommu_sva *handle = ERR_PTR(-EINVAL);
+	const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+	if (!ops || !ops->sva_bind)
+		return ERR_PTR(-ENODEV);
+
+	group = iommu_group_get(dev);
+	if (!group)
+		return ERR_PTR(-ENODEV);
+
+	/* Ensure device count and domain don't change while we're binding */
+	mutex_lock(&group->mutex);
+
+	/*
+	 * To keep things simple, SVA currently doesn't support IOMMU groups
+	 * with more than one device. Existing SVA-capable systems are not
+	 * affected by the problems that required IOMMU groups (lack of ACS
+	 * isolation, device ID aliasing and other hardware issues).
+	 */
+	if (iommu_group_device_count(group) != 1)
+		goto out_unlock;
+
+	handle = ops->sva_bind(dev, mm, drvdata);
+
+out_unlock:
+	mutex_unlock(&group->mutex);
+	iommu_group_put(group);
+
+	return handle;
+}
+EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
+
+/**
+ * iommu_sva_unbind_device() - Remove a bond created with iommu_sva_bind_device
+ * @handle: the handle returned by iommu_sva_bind_device()
+ *
+ * Put reference to a bond between device and address space. The device should
+ * not be issuing any more transaction for this PASID. All outstanding page
+ * requests for this PASID must have been flushed to the IOMMU.
+ *
+ * Returns 0 on success, or an error value
+ */
+void iommu_sva_unbind_device(struct iommu_sva *handle)
+{
+	struct iommu_group *group;
+	struct device *dev = handle->dev;
+	const struct iommu_ops *ops = dev->bus->iommu_ops;
+
+	if (!ops || !ops->sva_unbind)
+		return;
+
+	group = iommu_group_get(dev);
+	if (!group)
+		return;
+
+	mutex_lock(&group->mutex);
+	ops->sva_unbind(handle);
+	mutex_unlock(&group->mutex);
+
+	iommu_group_put(group);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
+
+int iommu_sva_set_ops(struct iommu_sva *handle,
+		      const struct iommu_sva_ops *sva_ops)
+{
+	if (handle->ops && handle->ops != sva_ops)
+		return -EEXIST;
+
+	handle->ops = sva_ops;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iommu_sva_set_ops);
+
+int iommu_sva_get_pasid(struct iommu_sva *handle)
+{
+	const struct iommu_ops *ops = handle->dev->bus->iommu_ops;
+
+	if (!ops || !ops->sva_get_pasid)
+		return IOMMU_PASID_INVALID;
+
+	return ops->sva_get_pasid(handle);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);