1 files changed, 41 insertions, 7 deletions

diff --git a/drivers/xen/grant-dma-ops.c b/drivers/xen/grant-dma-ops.c
index aaff35cda517..fc0142484001 100644
--- a/drivers/xen/grant-dma-ops.c
+++ b/drivers/xen/grant-dma-ops.c
@@ -56,11 +56,6 @@ static struct xen_grant_dma_data *find_xen_grant_dma_data(struct device *dev)
  * Such a DMA address is formed by using the grant reference as a frame
  * number and setting the highest address bit (this bit is for the backend
  * to be able to distinguish it from e.g. a mmio address).
- *
- * Note that for now we hard wire dom0 to be the backend domain. In order
- * to support any domain as backend we'd need to add a way to communicate
- * the domid of this backend, e.g. via Xenstore, via the PCI-device's
- * config space or DT/ACPI.
  */
 static void *xen_grant_dma_alloc(struct device *dev, size_t size,
 				 dma_addr_t *dma_handle, gfp_t gfp,
@@ -276,9 +271,26 @@ static const struct dma_map_ops xen_grant_dma_ops = {
 	.dma_supported = xen_grant_dma_supported,
 };
 
+bool xen_is_grant_dma_device(struct device *dev)
+{
+	struct device_node *iommu_np;
+	bool has_iommu;
+
+	/* XXX Handle only DT devices for now */
+	if (!dev->of_node)
+		return false;
+
+	iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
+	has_iommu = iommu_np && of_device_is_compatible(iommu_np, "xen,grant-dma");
+	of_node_put(iommu_np);
+
+	return has_iommu;
+}
+
 void xen_grant_setup_dma_ops(struct device *dev)
 {
 	struct xen_grant_dma_data *data;
+	struct of_phandle_args iommu_spec;
 
 	data = find_xen_grant_dma_data(dev);
 	if (data) {
@@ -286,12 +298,34 @@ void xen_grant_setup_dma_ops(struct device *dev)
 		return;
 	}
 
+	/* XXX ACPI device unsupported for now */
+	if (!dev->of_node)
+		goto err;
+
+	if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells",
+			0, &iommu_spec)) {
+		dev_err(dev, "Cannot parse iommus property\n");
+		goto err;
+	}
+
+	if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
+			iommu_spec.args_count != 1) {
+		dev_err(dev, "Incompatible IOMMU node\n");
+		of_node_put(iommu_spec.np);
+		goto err;
+	}
+
+	of_node_put(iommu_spec.np);
+
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		goto err;
 
-	/* XXX The dom0 is hardcoded as the backend domain for now */
-	data->backend_domid = 0;
+	/*
+	 * The endpoint ID here means the ID of the domain where the corresponding
+	 * backend is running
+	 */
+	data->backend_domid = iommu_spec.args[0];
 
 	if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data,
 			GFP_KERNEL))) {