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

[Eric Auger]

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.au...@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

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