[PATCH v13 13/13] vfio/pci: Inject page response upon response region fill

[Eric Auger]

When the userspace increments the head of the page response
buffer ring, let's push the response into the iommu layer.
This is done through a workqueue that pops the responses from
the ring buffer and increment the tail.

Signed-off-by: Eric Auger <eric.au...@redhat.com>
---
 drivers/vfio/pci/vfio_pci.c         | 40 +++++++++++++++++++++++++++++
 drivers/vfio/pci/vfio_pci_private.h |  7 +++++
 drivers/vfio/pci/vfio_pci_rdwr.c    |  1 +
 3 files changed, 48 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 560b1a830726..bb4a0e1e39bf 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -552,6 +552,32 @@ static int vfio_pci_dma_fault_init(struct vfio_pci_device 
*vdev)
        return ret;
 }
 
+static void dma_response_inject(struct work_struct *work)
+{
+       struct vfio_pci_dma_fault_response_work *rwork =
+               container_of(work, struct vfio_pci_dma_fault_response_work, 
inject);
+       struct vfio_region_dma_fault_response *header = rwork->header;
+       struct vfio_pci_device *vdev = rwork->vdev;
+       struct iommu_page_response *resp;
+       u32 tail, head, size;
+
+       mutex_lock(&vdev->fault_response_queue_lock);
+
+       tail = header->tail;
+       head = header->head;
+       size = header->nb_entries;
+
+       while (CIRC_CNT(head, tail, size) >= 1) {
+               resp = (struct iommu_page_response 
*)(vdev->fault_response_pages + header->offset +
+                                               tail * header->entry_size);
+
+               /* TODO: properly handle the return value */
+               iommu_page_response(&vdev->pdev->dev, resp);
+               header->tail = tail = (tail + 1) % size;
+       }
+       mutex_unlock(&vdev->fault_response_queue_lock);
+}
+
 #define DMA_FAULT_RESPONSE_RING_LENGTH 512
 
 static int vfio_pci_dma_fault_response_init(struct vfio_pci_device *vdev)
@@ -597,8 +623,22 @@ static int vfio_pci_dma_fault_response_init(struct 
vfio_pci_device *vdev)
        header->nb_entries = DMA_FAULT_RESPONSE_RING_LENGTH;
        header->offset = PAGE_SIZE;
 
+       vdev->response_work = kzalloc(sizeof(*vdev->response_work), GFP_KERNEL);
+       if (!vdev->response_work)
+               goto out;
+       vdev->response_work->header = header;
+       vdev->response_work->vdev = vdev;
+
+       /* launch the thread that will extract the response */
+       INIT_WORK(&vdev->response_work->inject, dma_response_inject);
+       vdev->dma_fault_response_wq =
+               create_singlethread_workqueue("vfio-dma-fault-response");
+       if (!vdev->dma_fault_response_wq)
+               return -ENOMEM;
+
        return 0;
 out:
+       kfree(vdev->fault_response_pages);
        vdev->fault_response_pages = NULL;
        return ret;
 }
diff --git a/drivers/vfio/pci/vfio_pci_private.h 
b/drivers/vfio/pci/vfio_pci_private.h
index f7b1e7fb86e5..835fbb221dea 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -52,6 +52,12 @@ struct vfio_pci_irq_ctx {
        struct irq_bypass_producer      producer;
 };
 
+struct vfio_pci_dma_fault_response_work {
+       struct work_struct inject;
+       struct vfio_region_dma_fault_response *header;
+       struct vfio_pci_device *vdev;
+};
+
 struct vfio_pci_device;
 struct vfio_pci_region;
 
@@ -146,6 +152,7 @@ struct vfio_pci_device {
        u8                      *fault_pages;
        u8                      *fault_response_pages;
        struct workqueue_struct *dma_fault_response_wq;
+       struct vfio_pci_dma_fault_response_work *response_work;
        struct mutex            fault_queue_lock;
        struct mutex            fault_response_queue_lock;
        struct list_head        dummy_resources_list;
diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index efde0793360b..78c494fe35cc 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -430,6 +430,7 @@ size_t vfio_pci_dma_fault_response_rw(struct 
vfio_pci_device *vdev, char __user
                mutex_lock(&vdev->fault_response_queue_lock);
                header->head = new_head;
                mutex_unlock(&vdev->fault_response_queue_lock);
+               queue_work(vdev->dma_fault_response_wq, 
&vdev->response_work->inject);
        } else {
                if (copy_to_user(buf, base + pos, count))
                        return -EFAULT;
-- 
2.26.3