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    SubjectRe: [RFC PATCH v1 3/4] vfio: Try to enable IOPF for VFIO devices
    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,

    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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