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    Subject[PATCH v11 05/13] vfio/pci: Register an iommu fault handler
    Date
    Register an IOMMU fault handler which records faults in
    the DMA FAULT region ring buffer. In a subsequent patch, we
    will add the signaling of a specific eventfd to allow the
    userspace to be notified whenever a new fault as shown up.

    Signed-off-by: Eric Auger <eric.auger@redhat.com>

    ---
    v11 -> v12:
    - take the fault_queue_lock before reading header (Zenghui)
    - also record recoverable errors

    v10 -> v11:
    - move iommu_unregister_device_fault_handler into
    vfio_pci_disable
    - check fault_pages != 0

    v8 -> v9:
    - handler now takes an iommu_fault handle
    - eventfd signaling moved to a subsequent patch
    - check the fault type and return an error if != UNRECOV
    - still the fault handler registration can fail. We need to
    reach an agreement about how to deal with the situation

    v3 -> v4:
    - move iommu_unregister_device_fault_handler to vfio_pci_release
    ---
    drivers/vfio/pci/vfio_pci.c | 45 +++++++++++++++++++++++++++++++++++++
    1 file changed, 45 insertions(+)

    diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
    index 7546a81e7fb6..b39d6ed66c71 100644
    --- a/drivers/vfio/pci/vfio_pci.c
    +++ b/drivers/vfio/pci/vfio_pci.c
    @@ -27,6 +27,7 @@
    #include <linux/vgaarb.h>
    #include <linux/nospec.h>
    #include <linux/sched/mm.h>
    +#include <linux/circ_buf.h>

    #include "vfio_pci_private.h"

    @@ -335,6 +336,41 @@ static const struct vfio_pci_regops vfio_pci_dma_fault_regops = {
    .add_capability = vfio_pci_dma_fault_add_capability,
    };

    +int vfio_pci_iommu_dev_fault_handler(struct iommu_fault *fault, void *data)
    +{
    + struct vfio_pci_device *vdev = (struct vfio_pci_device *)data;
    + struct vfio_region_dma_fault *reg =
    + (struct vfio_region_dma_fault *)vdev->fault_pages;
    + struct iommu_fault *new;
    + u32 head, tail, size;
    + int ret = -EINVAL;
    +
    +
    + if (WARN_ON(!reg))
    + return ret;
    +
    + mutex_lock(&vdev->fault_queue_lock);
    +
    + head = reg->head;
    + tail = reg->tail;
    + size = reg->nb_entries;
    +
    + new = (struct iommu_fault *)(vdev->fault_pages + reg->offset +
    + head * reg->entry_size);
    +
    + if (CIRC_SPACE(head, tail, size) < 1) {
    + ret = -ENOSPC;
    + goto unlock;
    + }
    +
    + *new = *fault;
    + reg->head = (head + 1) % size;
    + ret = 0;
    +unlock:
    + mutex_unlock(&vdev->fault_queue_lock);
    + return ret;
    +}
    +
    #define DMA_FAULT_RING_LENGTH 512

    static int vfio_pci_dma_fault_init(struct vfio_pci_device *vdev)
    @@ -376,6 +412,13 @@ static int vfio_pci_dma_fault_init(struct vfio_pci_device *vdev)
    header->entry_size = sizeof(struct iommu_fault);
    header->nb_entries = DMA_FAULT_RING_LENGTH;
    header->offset = sizeof(struct vfio_region_dma_fault);
    +
    + ret = iommu_register_device_fault_handler(&vdev->pdev->dev,
    + vfio_pci_iommu_dev_fault_handler,
    + vdev);
    + if (ret) /* the dma fault region is freed in vfio_pci_disable() */
    + goto out;
    +
    return 0;
    out:
    kfree(vdev->fault_pages);
    @@ -508,6 +551,8 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
    VFIO_IRQ_SET_ACTION_TRIGGER,
    vdev->irq_type, 0, 0, NULL);

    + WARN_ON(iommu_unregister_device_fault_handler(&vdev->pdev->dev));
    +
    /* Device closed, don't need mutex here */
    list_for_each_entry_safe(ioeventfd, ioeventfd_tmp,
    &vdev->ioeventfds_list, next) {
    --
    2.21.3
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