[PATCH v4 19/22] vfio-pci: Register an iommu fault handler

[Eric Auger <eric.auger@redhat.com>]

This patch registers a fault handler which records faults in
a circular buffer and then signals an eventfd. This buffer is
exposed within the fault region.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c         | 49 +++++++++++++++++++++++++++++
 drivers/vfio/pci/vfio_pci_private.h |  1 +
 2 files changed, 50 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index aaf63e5ca2b6..019c9fd380a5 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -29,6 +29,7 @@
 #include <linux/vfio.h>
 #include <linux/vgaarb.h>
 #include <linux/nospec.h>
+#include <linux/circ_buf.h>
 
 #include "vfio_pci_private.h"
 
@@ -244,6 +245,46 @@ static const struct vfio_pci_regops vfio_pci_fault_prod_regops = {
 	.add_capability = vfio_pci_fault_prod_add_capability,
 };
 
+int vfio_pci_iommu_dev_fault_handler(struct iommu_fault_event *evt, void *data)
+{
+	struct vfio_pci_device *vdev = (struct vfio_pci_device *) data;
+	struct vfio_region_fault_prod *prod_region =
+		(struct vfio_region_fault_prod *)vdev->fault_pages;
+	struct vfio_region_fault_cons *cons_region =
+		(struct vfio_region_fault_cons *)(vdev->fault_pages + 2 * PAGE_SIZE);
+	struct iommu_fault *new =
+		(struct iommu_fault *)(vdev->fault_pages + prod_region->offset +
+			prod_region->prod * prod_region->entry_size);
+	int prod, cons, size;
+
+	mutex_lock(&vdev->fault_queue_lock);
+
+	if (!vdev->fault_abi)
+		goto unlock;
+
+	prod = prod_region->prod;
+	cons = cons_region->cons;
+	size = prod_region->nb_entries;
+
+	if (CIRC_SPACE(prod, cons, size) < 1)
+		goto unlock;
+
+	*new = evt->fault;
+	prod = (prod + 1) % size;
+	prod_region->prod = prod;
+	mutex_unlock(&vdev->fault_queue_lock);
+
+	mutex_lock(&vdev->igate);
+	if (vdev->dma_fault_trigger)
+		eventfd_signal(vdev->dma_fault_trigger, 1);
+	mutex_unlock(&vdev->igate);
+	return 0;
+
+unlock:
+	mutex_unlock(&vdev->fault_queue_lock);
+	return -EINVAL;
+}
+
 static int vfio_pci_init_fault_region(struct vfio_pci_device *vdev)
 {
 	struct vfio_region_fault_prod *header;
@@ -276,6 +317,13 @@ static int vfio_pci_init_fault_region(struct vfio_pci_device *vdev)
 	header = (struct vfio_region_fault_prod *)vdev->fault_pages;
 	header->version = -1;
 	header->offset = PAGE_SIZE;
+
+	ret = iommu_register_device_fault_handler(&vdev->pdev->dev,
+					vfio_pci_iommu_dev_fault_handler,
+					vdev);
+	if (ret)
+		goto out;
+
 	return 0;
 out:
 	kfree(vdev->fault_pages);
@@ -1420,6 +1468,7 @@ static void vfio_pci_remove(struct pci_dev *pdev)
 	vfio_iommu_group_put(pdev->dev.iommu_group, &pdev->dev);
 	kfree(vdev->region);
 	kfree(vdev->fault_pages);
+	iommu_unregister_device_fault_handler(&pdev->dev);
 	mutex_destroy(&vdev->ioeventfds_lock);
 	kfree(vdev);
 
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 047708aaad66..6f4309c4fe87 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -120,6 +120,7 @@ struct vfio_pci_device {
 	int			ioeventfds_nr;
 	struct eventfd_ctx	*err_trigger;
 	struct eventfd_ctx	*req_trigger;
+	struct eventfd_ctx	*dma_fault_trigger;
 	struct mutex		fault_queue_lock;
 	int			fault_abi;
 	struct list_head	dummy_resources_list;
-- 
2.20.1