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SubjectRe: [RFC PATCH v1 3/4] vfio: Try to enable IOPF for VFIO devices
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On 2021/1/30 6:42, Alex Williamson wrote:
> On Mon, 25 Jan 2021 17:04:01 +0800
> Shenming Lu <lushenming@huawei.com> wrote:
>
>> If IOMMU_DEV_FEAT_IOPF is set for the VFIO device, which means that
>> the delivering of page faults of this device from the IOMMU is enabled,
>> we register the VFIO page fault handler to complete the whole faulting
>> path (HW+SW). And add a iopf_enabled field in struct vfio_device to
>> record it.
>>
>> Signed-off-by: Shenming Lu <lushenming@huawei.com>
>> ---
>> drivers/vfio/vfio.c | 20 ++++++++++++++++++++
>> 1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
>> index ff7797260d0f..fd885d99ee0f 100644
>> --- a/drivers/vfio/vfio.c
>> +++ b/drivers/vfio/vfio.c
>> @@ -97,6 +97,7 @@ struct vfio_device {
>> struct vfio_group *group;
>> struct list_head group_next;
>> void *device_data;
>> + bool iopf_enabled;
>> };
>>
>> #ifdef CONFIG_VFIO_NOIOMMU
>> @@ -532,6 +533,21 @@ static struct vfio_group *vfio_group_get_from_dev(struct device *dev)
>> /**
>> * Device objects - create, release, get, put, search
>> */
>> +
>> +static void vfio_device_enable_iopf(struct vfio_device *device)
>> +{
>> + struct device *dev = device->dev;
>> +
>> + if (!iommu_dev_has_feature(dev, IOMMU_DEV_FEAT_IOPF))
>> + return;
>> +
>> + if (WARN_ON(iommu_register_device_fault_handler(dev,
>> + vfio_iommu_dev_fault_handler, dev)))
>
> The layering here is wrong, vfio-core doesn't manage the IOMMU, we have
> backend IOMMU drivers for that. We can't even assume we have IOMMU API
> support here, that's what the type1 backend handles. Thanks,

Thanks for pointing it out, I will correct it: maybe do the enabling via
the VFIO_IOMMU_ENABLE_IOPF ioctl mentioned in the cover and suggest the
user to call it before VFIO_IOMMU_MAP_DMA, also move the iopf_enabled field
from struct vfio_device to struct vfio_iommu...

Thanks,
Shenming

>
> Alex
>
>> + return;
>> +
>> + device->iopf_enabled = true;
>> +}
>> +
>> static
>> struct vfio_device *vfio_group_create_device(struct vfio_group *group,
>> struct device *dev,
>> @@ -549,6 +565,8 @@ struct vfio_device *vfio_group_create_device(struct vfio_group *group,
>> device->group = group;
>> device->ops = ops;
>> device->device_data = device_data;
>> + /* By default try to enable IOPF */
>> + vfio_device_enable_iopf(device);
>> dev_set_drvdata(dev, device);
>>
>> /* No need to get group_lock, caller has group reference */
>> @@ -573,6 +591,8 @@ static void vfio_device_release(struct kref *kref)
>> mutex_unlock(&group->device_lock);
>>
>> dev_set_drvdata(device->dev, NULL);
>> + if (device->iopf_enabled)
>> + WARN_ON(iommu_unregister_device_fault_handler(device->dev));
>>
>> kfree(device);
>>
>
> .
>

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