[RFC v7 17/26] vfio/pci: Implement the DMA fault handler

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

Whenever the eventfd is triggered, we retrieve the DMA fault(s)
from the mmapped fault region and inject them in the iommu
memory region.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 hw/vfio/pci.h |  1 +
 hw/vfio/pci.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
index d6cc689f5e..350e9e9005 100644
--- a/hw/vfio/pci.h
+++ b/hw/vfio/pci.h
@@ -146,6 +146,7 @@ struct VFIOPCIDevice {
     EventNotifier req_notifier;
     VFIOPCIExtIRQ *ext_irqs;
     VFIORegion dma_fault_region;
+    uint32_t fault_tail_index;
     int (*resetfn)(struct VFIOPCIDevice *);
     uint32_t vendor_id;
     uint32_t device_id;
diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 35551bfd1d..4e3495bb60 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2891,10 +2891,60 @@ static PCIPASIDOps vfio_pci_pasid_ops = {
 static void vfio_dma_fault_notifier_handler(void *opaque)
 {
     VFIOPCIExtIRQ *ext_irq = opaque;
+    VFIOPCIDevice *vdev = ext_irq->vdev;
+    PCIDevice *pdev = &vdev->pdev;
+    AddressSpace *as = pci_device_iommu_address_space(pdev);
+    IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(as->root);
+    struct vfio_region_dma_fault header;
+    struct iommu_fault *queue;
+    char *queue_buffer = NULL;
+    ssize_t bytes;
 
     if (!event_notifier_test_and_clear(&ext_irq->notifier)) {
         return;
     }
+
+    bytes = pread(vdev->vbasedev.fd, &header, sizeof(header),
+                  vdev->dma_fault_region.fd_offset);
+    if (bytes != sizeof(header)) {
+        error_report("%s unable to read the fault region header (0x%lx)",
+                     __func__, bytes);
+        return;
+    }
+
+    /* Normally the fault queue is mmapped */
+    queue = (struct iommu_fault *)vdev->dma_fault_region.mmaps[0].mmap;
+    if (!queue) {
+        size_t queue_size = header.nb_entries * header.entry_size;
+
+        error_report("%s: fault queue not mmapped: slower fault handling",
+                     vdev->vbasedev.name);
+
+        queue_buffer = g_malloc(queue_size);
+        bytes =  pread(vdev->vbasedev.fd, queue_buffer, queue_size,
+                       vdev->dma_fault_region.fd_offset + header.offset);
+        if (bytes != queue_size) {
+            error_report("%s unable to read the fault queue (0x%lx)",
+                         __func__, bytes);
+            return;
+        }
+
+        queue = (struct iommu_fault *)queue_buffer;
+    }
+
+    while (vdev->fault_tail_index != header.head) {
+        memory_region_inject_faults(iommu_mr, 1,
+                                    &queue[vdev->fault_tail_index]);
+        vdev->fault_tail_index =
+            (vdev->fault_tail_index + 1) % header.nb_entries;
+    }
+    bytes = pwrite(vdev->vbasedev.fd, &vdev->fault_tail_index, 4,
+                   vdev->dma_fault_region.fd_offset);
+    if (bytes != 4) {
+        error_report("%s unable to write the fault region tail index (0x%lx)",
+                     __func__, bytes);
+    }
+    g_free(queue_buffer);
 }
 
 static int vfio_register_ext_irq_handler(VFIOPCIDevice *vdev,
-- 
2.21.3