Hi Zenghui,
On 9/24/20 10:49 AM, Zenghui Yu wrote:
> Hi Eric,
>
> On 2020/3/21 0:19, Eric Auger wrote:
>> 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@xxxxxxxxxx>
>
> [...]
>
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index 586b89debed5..69595c240baf 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -27,6 +27,7 @@
>> #include <linux/vfio.h>
>> #include <linux/vgaarb.h>
>> #include <linux/nospec.h>
>> +#include <linux/circ_buf.h>
>> #include "vfio_pci_private.h"
>> @@ -283,6 +284,38 @@ 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 =
>> + (struct iommu_fault *)(vdev->fault_pages + reg->offset +
>> + reg->head * reg->entry_size);
>
> Shouldn't 'reg->head' be protected under the fault_queue_lock? Otherwise
> things may change behind our backs...>
> We shouldn't take any assumption about how IOMMU driver would report the
> fault (serially or in parallel), I think.
Yes I modified the locking
Thanks
Eric
>
>> + int head, tail, size;
>> + int ret = 0;
>> +
>> + if (fault->type != IOMMU_FAULT_DMA_UNRECOV)
>> + return -ENOENT;
>> +
>> + mutex_lock(&vdev->fault_queue_lock);
>> +
>> + head = reg->head;
>> + tail = reg->tail;
>> + size = reg->nb_entries;
>> +
>> + if (CIRC_SPACE(head, tail, size) < 1) {
>> + ret = -ENOSPC;
>> + goto unlock;
>> + }
>> +
>> + *new = *fault;
>> + reg->head = (head + 1) % size;
>> +unlock:
>> + mutex_unlock(&vdev->fault_queue_lock);
>> + return ret;
>> +}
>> +
>> #define DMA_FAULT_RING_LENGTH 512
>> static int vfio_pci_init_dma_fault_region(struct vfio_pci_device
>> *vdev)
>> @@ -317,6 +350,13 @@ static int vfio_pci_init_dma_fault_region(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)
>> + goto out;
>> +
>> return 0;
>> out:
>> kfree(vdev->fault_pages);
>
>
> Thanks,
> Zenghui
>
